Physiology LC7 Resistance of the Body to Infection-Leukocytes PDF

A. CONCENTRATIONS OF THE DIFFERENT WBC IN THE BLOOD OUTLINE - The adult human being has about 7,000 WBCs per microliter of blood I. W...

A. CONCENTRATIONS OF THE DIFFERENT WBC IN THE BLOOD OUTLINE - The adult human being has about 7,000 WBCs per microliter of blood I. WHITE BLOOD CELLS Table 1. Normal Percentages of the different types of WBCs per microliter of A. CONCENTRATIONS OF THE DIFFERENT WBC blood. IN THE BLOOD B. GENESIS OF WHITE BLOOD CELLS Type of WBC Percentage C. IMPORTANCE OF WHITE BLOOD CELLS i. DIAPEDESIS Polymorphonuclear Neutrophils 62.0% ii. AMEBOID MOVEMENT iii. CHEMOTAXIS Polymorphonuclear Eosinophils 2.3% II. PHAGOCYTOSIS A. STAGES OF PHAGOCYTOSIS Polymorphonuclear Basophils 0.4% III. MONOCYTE-MACROPHAGE CELL SYSTEM (RETICULOENDOTHELIAL SYSTEM) Monocytes 5.3% IV. INFLAMMATION A. INFLAMMATION PROCESS B. CHARACTERISTICS OF INFLAMMATION Lymphocytes 30.0% C. PURPOSE OF INFLAMMATION V. THE “WALLING-OFF” EFFECT - Lymphocytes are formed in different lymphogenous tissues VI. FIRST LINE OF DEFENSE: TISSUE MACROPHAGE especially the lymph glands, spleen, thymus, tonsils, and various VII. SECOND LINE OF INVASION: NEUTROPHIL INVASION OF pockets of lymphoid tissue elsewhere in the body, such as in the THE INFLAMED AREA bone marrow and in so-called Peyer’s patches underneath the VIII. THIRD LINE OF DEFENSE: SECOND MACROPHAGE epithelium in the gut wall. INVASION INTO THE INFLAMED TISSUE - The WBCs formed in the bone marrow are stored within the marrow IX. FOURTH LINE OF DEFENSE: INCREASED PRODUCTION until they are needed in the circulatory system. Then, when the need OF GRANULOCYTES AND MONOCYTES BY THE BONE arises, various factors cause them to be released MARROW - Normally, about three times as many WBCs are stored in the marrow X. FORMATION OF PUS as circulate in the entire blood. This quantity represents about a XI. EOSINOPHILS 6-day supply of these cells. XII. BASOPHILS - The lymphocytes are mostly stored in the various lymphoid tissues, XIII. LEUKOPENIA except for a small number that are temporarily being transported in XIV. LEUKEMIA the blood. Neutrophils ○ Represent the majority of the five white blood cells in the I. WHITE BLOOD CELLS body. ○ Act as scavengers ○ Help surrounds and destroys bacteria and fungi - Also known as LEUKOCYTES Lymphocytes - Are the mobile units of the body’s protective system ○ has two cell types: - Formed partially in the bone marrow (granulocytes) and monocytes B cells/B lymphocytes: produce antibody that and a few lymphocytes and partially in the lymph tissue helps the immune system mount an immune (lymphocytes and plasma cells). After formation, they are response to infection transported in the blood to different body parts. T cells/T lymphocytes: help recognize and - Five types of white blood cells (WBC) remove the infection causing cells ○ Granulocytes Monocytes Granular appearance ○ makes about 2-8% of the total WBC count, average of Polymorphonuclear cells (multiple nuclei) 5.8% Neutrophils, eosinophils, and basophils ○ present when the body fights chronic infection ○ Agranulocytes ○ precursor of dendritic cells and macrophages Called as such because they do not have Eosinophils cytoplasmic granules ○ Responding to infections caused by parasites Monocytes and lymphocytes Basophils ○ Least common type (represent less than 1%) ○ Typically seen in an allergic reaction and with mast ce Figure 1. Different types of WBCs. Page 1 of 8 [PHYSIOLOGY] 1.07 RESISTANCE OF THE BODY TO INFECTION-LEUKOCYTES - Dr. Ma. Eileen Pascua The real value of WBCs is that most of them are specifically B. GENESIS OF WHITE BLOOD CELLS transported to areas of serious infection and inflammation, thereby providing a rapid and potent defense against infectious agents. We are constantly exposed to bacteria, viruses, fungi, parasites, all of which do normally occur and vary in degrees that are found in the skin, in the mouth, in the respiratory passages, intestinal lining, urinary tract, lining in the membranes of the eyes, and we call them as the normal body flora. However, there are times that many of these organisms are capable of causing abnormal physiologic function or even death if they invade the deeper tissues and exposes us down to a highly infectious or little diseases like septicemia, pneumonia, meningitis, urosepsis, typhoid, etc. Once the inflammation has begun, the neutrophil makes the first wave of cells that crosses the cell. After this, the monocyte also crosses the blood vessels and differentiates that into macrophage. a. Neutrophils and monocytes can squeeze through the pores of the blood capillaries by DIAPEDESIS Diapedesis: process of rolling and squeezing movement of the leukocyte between the cells and the capillary walls and out of the blood vessels. Even though a pore is much smaller than a cell, a small portion of the BONE MARROW LYMPHOGENOUS TISSUE cell slides through the pore at a time; the portion sliding through is Figure 2. Genesis of myelocytes and lymphocytes with their respective locations. momentarily constricted to the size of the pore. Extravasation/Transmigration: process of the leukocyte leaving the In Figure 2, Cell 3 represents megakaryocytes which fragment in the bloodstream and entering into the tissue bone marrow. These small fragments are known as platelets (thrombocytes) and are then passed into the blood. Platelets are b. WBC’s move through tissue spaces by AMEBOID MOVEMENT very important in the initiation of blood clots Both neutrophils and macrophages can move through the tissues by Figure 2 shows the two lineages of WBC: myelocytic and ameboid motion lymphocytic ○ Myelocytic lineage (refer to Figure 2) c. WBCs are attracted to inflamed tissues by CHEMOTAXIS 1) Myeloblast formation in the bone marrow Chemotaxis is the process of neutrophils traveling to the site where 2) Promyelocyte they are needed and it occurs after the diapedesis 3) Megakaryocyte Groups of WBCs are attracted to the inflamed tissue areas because of 4) Neutrophil myelocyte these chemical substances. Both the neutrophils and the monocytes 5) Young neutrophil metamyelocyte go into the site of this chemical called chemotaxis source. 6) “Band” neutrophil metamyelocyte Chemotactic substance/chemokine: a soluble chemical mediator 7) Polymorphonuclear neutrophil that has the function to attract the cells towards the site of 8) Eosinophil myelocyte inflammation. 9) Eosinophil metamyelocyte When a tissue becomes inflamed at least a dozen different products 10) Polymorphonuclear eosinophil that can cause chemotaxis toward the inflamed area are formed: 11) Basophil myelocyte ○ bacterial or viral toxins 12) Polymorphonuclear basophil ○ degenerative products of the inflamed tissues reaction 13)-16) Stages of monocyte formation products of the “complement complex” activated in The granulocytes and the monocytes are formed in the bone inflamed tissues marrow, whereas for the lymphocytes and the plasma cells, they are ○ reaction products caused by plasma clotting in the formed in the different lymphogenous tissues. inflamed area ○ other substances C. IMPORTANCE OF WHITE BLOOD CELLS Our bodies have a special system for combating the different Chemotaxis depends on the concentration gradient of the chemotactic infectious and toxic agents. substance. This system is composed of blood leukocytes (WBC) and tissue cells Most cells that exhibit ameboid locomotion move toward the source derived from leukocytes. of a chemotactic substance, that is, from an area of lower These cells work together in two ways to prevent diseases: concentration toward an area of higher concentration which is called 1. By destroying invading bacteria or viruses by phagocytosis positive chemotaxis. Some cells move away from the source, which - the function of the neutrophils and monocyte that turns is called negative chemotaxis. into macrophage wherein they ingest or engulf pathogen It is known that the side of the cell most exposed to the chemotactic and then they destroy them or eat them, digest substance develops membrane changes that cause pseudopodial them—we call it as phagocytosis protrusion. 2. By forming Antibodies and Sensitized lymphocytes that may destroy or inactivate the invader - function of lymphocytes, specifically the B cells that produce antibodies to destroy a particular pathogen and by the T cells that produce antitoxin. - Example: cytotoxin counteracts the toxin released by pathogen Page 2 of 8 [PHYSIOLOGY] 1.07 RESISTANCE OF THE BODY TO INFECTION-LEUKOCYTES - Dr. Ma. Eileen Pascua Figure 5. Macrophage. A. STAGES OF PHAGOCYTOSIS Figure 3. Movement of neutrophils through the pores of capillaries by diapedesis and toward an area of tissue damage by chemotaxis. II. PHAGOCYTOSIS The most important function of the neutrophils and macrophages is phagocytosis – “cellular ingestion of the offending agent” is a process by which a solid material, for example: pathogen or bacteria, are ingested by the cell (WBC) via endocytosis. Figure 6. Process of Phagocytosis. The pathogens – bacteria, are ingested via endocytosis. By means of chemotaxis, the microbe will now adhere to the phagocyte. Ingestion of the microbe by the phagocytic cell and formation of the phagosome or otherwise known as the phagocytic vesicle. Lysosomes contain different digestive enzymes. The fusion of this lysosome with the phagosome will now create the phagolysosome. Figure 4. Phagocytosis. Digestion now starts of the ingested microbes by the digestive enzymes and then what will remain are the indigestible materials A single neutrophil can usually phagocytize 3-20 bacteria before the inside the residual body. neutrophil becomes inactivated and dies These wastes are now discharged Macrophages are the end-stage product of monocytes that enter the tissues from the blood. Whether phagocytosis will occur depends on this THREE SELECTIVE ○ They are much more powerful phagocytes than PROCEDURES: neutrophils, often capable of phagocytizing as many as 1. Most natural structures in the tissues have smooth surfaces, which 100 bacteria. resist phagocytosis. However, if the surface is rough, the likelihood of ○ Monocytes = still in the circulation. Once it enters into the phagocytosis is increased. tissues, it now becomes the macrophage 2. Most natural substances of the body have protective protein coats ○ irregularly shaped phagocyte that is amoebic in nature that repel the phagocytes. Conversely, most dead tissues and foreign ○ most versatile of the phagocytes in the body particles have no protective coats, which makes them subject to ○ can move through the tissues; can squeeze through the phagocytosis. capillary walls via its pseudopodia 3. The immune system of the body develops antibodies against ○ can exist in many tissues of the body—either they freely infectious agents such as bacteria. The antibodies then adhere to the roam around to the connective tissues or they can be bacterial membranes and thereby make the bacteria especially fixed into the reticular fibers with the specific issues susceptible to phagocytosis. To do this, the antibody molecule also combines with the C3 product of the complement cascade. The C3 molecules, in turn, attach to receptors on the phagocyte membrane, thus initiating phagocytosis. This process by which a pathogen is selected for phagocytosis and destruction is called opsonization. Phagocytes must be selective of the materials that are phagocytized. Otherwise, even the normal cells and structures of the body might be ingested Page 3 of 8 [PHYSIOLOGY] 1.07 RESISTANCE OF THE BODY TO INFECTION-LEUKOCYTES - Dr. Ma. Eileen Pascua NEUTROPHILS AND MACROPHAGES CAN KILL BACTERIA FUNCTIONS: Much of the killing effect results from several powerful oxidizing Removal of foreign objects and toxins. agents formed by enzymes in the membrane of the phagosome or by Formation of new RBCs and WBCs. a special organelle called the (peroxisome) Destruction of senescent RBCs. ○ superoxide (O2− ) Formation of bile pigments. ○ hydrogen peroxide (H2O2) Storage of iron. ○ hydroxyl ions (OH−) Clearance of heparin via heparinase ○ lysosomal enzymes myeloperoxidase - catalyzes the reaction between H2O2 and chloride ions to form IV. INFLAMMATION hypochlorite, which is exceedingly bactericidal. When tissue injury occurs, whether caused by bacteria, trauma, chemicals, heat or any other phenomenon, multiple substances are released by the bruised tissues and cause dramatic secondary changes in the surrounding undamaged tissues. The entire complex tissue changes is called INFLAMMATION It is the body’s response to infection or injury. Function: To destroy or inactivate foreign invaders and to set stage for tissue repair. Chemokine prompts the neutrophils to undergo diapedesis and go to the site of inflammation and do phagocytosis. Different products of complement cascade, treatments, etc releases blood protein and clotting elements the blood and clotting begin at the wound site. This will prevent pathogens from spreading via Figure 7. Formation of oxidizing agents by the enzymes in the membranes of blood. It will continue until the pathogen is eliminated and the phagosomes or in peroxisomes. wound is repaired. A. INFLAMMATION PROCESS III. MONOCYTE-MACROPHAGE CELL SYSTEM (RETICULOENDOTHELIAL SYSTEM) The total combination of monocytes, mobile macrophages, fixed (tissue) macrophages, and a few specialized endothelial cells in the bone marrow, spleen, and lymph nodes (various lymphoid tissues) more commonly known as Reticuloendothelial system (RES) located in tissues especially in tissues containing large number of particles, toxins or other amount of substances that must be destroyed Figure 9. Process of Inflammation. In injury, the resident tissue macrophage acts first. Next, mast cells and the circulating basophils release a chemical called histamine. This histamine causes local vasodilation and increased capillary permeability to cause recruitment of the leukocytes to the inflamed region. Platelets cascade coagulation are now activated and release blood protein and clotting elements from the blood and clotting begins at the wound site. This will prevent pathogens from spreading via blood. Inflammatory response continues until the foreign materials are eliminated and the wound is repaired Figure 8. (Top) Differentiation of a monocyte to different types of cells; (bottom) Different fixed macrophages in their respective locations. Page 4 of 8 [PHYSIOLOGY] 1.07 RESISTANCE OF THE BODY TO INFECTION-LEUKOCYTES - Dr. Ma. Eileen Pascua 1. Allows the body to defend itself from invading microorganisms. B. CHARACTERISTICS OF INFLAMMATION The increase in vascular diameter, and the activated endothelial cells, results in leukocytes being able to attach to the endothelium, and then migrate into the tissues where they can attack pathogens. 2. Induces local blood clotting. This creates a physical barrier preventing the infection from spreading into the bloodstream. 3. Promotes repair of injured tissue. Figure 10. Characteristics of Inflammation. Figure 13. (Left) Blood clotting beneath the damaged tissue; (Right) Tissue repair. V. THE “WALLING-OFF” EFFECT One of the first results of inflammation is to “wall off” areas of injury from the remaining tissues. The tissue spaces and the lymphatics in the inflamed area are blocked by fibrinogen clots, so that after a while, fluid barely flows through the spaces. Figure 11. Cardinal Signs of Inflammation. It delays the spread of bacteria or toxic products. This response helps to wall off infected areas to further spread and The inflammatory response initiated within hours of infection or allow the battle to focus at the inflammatory site. wounding is characterized by heat, redness, edema or swelling, tenderness or pain at the site of infection or injury. VI. FIRST LINE OF DEFENSE: TISSUE MACROPHAGE Four (4) cardinal signs of inflammation: 1. Heat (Calor) 2. Redness (Rubor) Within minutes after inflammation begins, the macrophages already 3. Swelling (Tumor) present in the tissues immediately begin their phagocytic actions. 4. Pain (Dolor) Next, many of the previously sessile macrophages break loose from 5. Loss of function (Functio laesa/5th characteristic) their attachments and become mobile, forming the first line of Due to increased vascular diameter (capillary widening) and defense against infection during the first hour or so. increased permeability. Increased vascular diameter will result in Examples of tissue macrophages: increased blood flow. (Heat and Redness). ○ Tissue Macrophages in the Skin and Subcutaneous The epithelial cell has gaps between, therefore fluid in the blood Tissues exceeds and then allows leakage in the interstitial space and When infection begins in a subcutaneous accumulation in the local tissue will now result in swelling. tissue and local inflammation starts, local Endothelial cells line the blood vessels and are activated during tissue macrophages can divide in situ and form inflammation and express molecules that promote attraction and still more macrophages. binding of these leukocytes. This will cause an increase in fibrinogen ○ Macrophages in the Lymph Nodes and other proteins leaking in the capillaries resulting in tenderness, If the particles are not destroyed locally in the pain and fever. tissues, they enter the lymph and flow to the lymph nodes located intermittently along the C. PURPOSE OF INFLAMMATION course of the lymph flow. The foreign particles are trapped in these nodes in a meshwork of sinuses lined by tissue macrophages. ○ Alveolar Macrophages in the Lungs Large numbers of tissue macrophages are present as integral components of the alveolar walls. They can phagocytize particles that become entrapped in the alveoli ○ Kupffer Cells in the Liver Sinusoids These cells form such an effective particulate Figure 12. Process of Extravasation. filtration system that almost none of the bacteria from the gastrointestinal tract pass Page 5 of 8 [PHYSIOLOGY] 1.07 RESISTANCE OF THE BODY TO INFECTION-LEUKOCYTES - Dr. Ma. Eileen Pascua from the portal blood into the general systemic Neutrophilia circulation. Within a few hours after the onset of acute, severe inflammation, the Phagocytosis by Kupffer cells have number of neutrophils in the blood increases 4-5 the normal (about demonstrated phagocytosis of a single 15 000 to 25 000 neutrophils per microliter). bacterium in less than 0.01 second. Caused by products of inflammation that enter the bloodstream, ○ Macrophages of the Spleen and Bone Marrow transported to the bone marrow, and act on the stored neutrophils Macrophages become entrapped by the of the marrow to mobilize these into the circulating blood and makes reticular meshwork of the two organs and even more neutrophils available to the inflamed area. when foreign particles come in contact with these macrophages, they are phagocytized. VIII. THIRD LINE OF DEFENSE: SECOND MACROPHAGE INVASION INTO THE INFLAMED TISSUE VII. SECOND LINE OF INVASION: NEUTROPHIL INVASION OF THE INFLAMED AREA Along with the invasion of neutrophils, monocytes from the blood enter the inflamed tissue and enlarge to become macrophages. The number of monocytes in the circulating blood is low and the Within the first hour or so after inflammation begins, a large number storage pool of monocytes in the bone marrow is much less than that of neutrophils begin to invade the inflamed area from the blood. of neutrophils. Therefore, the build-up of macrophages in the inflamed tissue area is much slower than that of neutrophils, PROCESS IN THE INVASION OF NEUTROPHILS TO THE INFLAMED AREA requiring several days to become effective. 1. They cause increased expression of adhesion molecules: selectins Even after invading the inflamed tissue, monocytes are still immature and intercellular adhesion molecule- 1 (ICAM-1) on the surface of cells, requiring 8 hours or more to swell to much larger sizes and endothelial cells in the capillaries and venules. develop tremendous quantities of lysosomes; only then do they acquire the full capacity of tissue macrophages for phagocytosis. After several days or weeks, the macrophages dominate the phagocytic cells of the inflamed area because of greatly increased bone marrow production of new monocytes. IX. FOURTH LINE OF DEFENSE: INCREASED PRODUCTION OF GRANULOCYTES AND MONOCYTES BY THE BONE MARROW This action results from stimulation of the granulocytic and monocytic progenitor cells of the marrow. However, it takes 3 to 4 days before newly formed granulocytes and monocytes reach the stage of leaving the bone marrow. Figure 14. The adhesion molecules P-Selectin and ICAM-1 on the endothelial If the stimulus from the inflamed tissue continues, the bone marrow cells. can continue to produce these cells in tremendous quantities for months and even years, sometimes at a rate 20 to 50 times normal 2. They cause the intercellular attachments between the endothelial (specially in chronic inflammation). cells of the capillaries and small venules to loosen, allowing openings to be large enough for neutrophils to crawl through directly from the Control of Macrophage blood into tissue spaces by diapedesis. Figure 15. Neutrophil squeezing out of the pores between endothelial cells. 3. They cause chemotaxis of the neutrophils toward the injured tissues. This invasion is caused by inflammatory cytokines TNF-a and IL-1 that Figure 16. Control of Macrophage. are produced in the inflamed tissue. This cytokine causes the endothelial cells to externalize a granule called Weibel Palade bodies The cause of increased production of granulocytes and monocytes by that contain the P-selectin. the bone marrow is mainly the three colony-stimulating factors, one Endothelial cell possesses different adhesion molecules: of which, GMCSF, G-CSF and M-CSF. ○ P-selectin – important for leukocyte recruitment same Combination of TNF, IL-1, and colony-stimulating factors provides a with ICAM-1 and leukocytes B-3 powerful feedback mechanism that begins with tissue inflammation ○ E-selectin and proceeds to formation of large numbers of defensive WBCs that ○ ICAM (intercellular adhesion molecules) help remove the cause of the inflammation. Page 6 of 8 [PHYSIOLOGY] 1.07 RESISTANCE OF THE BODY TO INFECTION-LEUKOCYTES - Dr. Ma. Eileen Pascua Both mast cells and basophils release an eosinophil chemotactic X. FORMATION OF PUS factor that causes eosinophils to migrate toward the inflamed allergic tissue. XII. BASOPHILS Figure 17. Formation of pus. When neutrophils and macrophages engulf large numbers of bacteria and necrotic tissue, essentially all the neutrophils and many, if not most, of the macrophages eventually die. Figure 19. Basophil. After several days, a cavity is often excavated in the inflamed tissues. This cavity contains varying portions of necrotic tissue, dead The basophils in the circulating blood are similar to the large tissue neutrophils, dead macrophages, and tissue fluid (the mixture is mast cells located immediately outside many of the capillaries in the commonly called pus). body. After the infection has been suppressed, the dead cells and necrotic Both mast cells & basophils liberate heparin (anticoagulant) into the tissue in the pus gradually autolyze over a period of days. blood which prevent coagulation The end products are eventually absorbed into the surrounding Both release histamine, smaller amt. of bradykinin and serotonin tissues and lymph until most of the evidence of tissue damage is (allergic reactions, pain, emotions) gone. Both play an important role in allergic reactions The whitish yellow or yellow brown or greenish color of the pus is IgE has a special propensity to attach to mast cells & basophils. The because of the accumulation of dead neutrophils. Sometimes it resulting attachment of antigen to antibody causes the mast cell or appears green because neutrophil produces green antibacterial basophil to rupture and release large quantities of histamine, protein called myeloperoxidase. bradykinin, serotonin, heparin, slow-reacting substance of Pseudomonas aeruginosa produces green pigment anaphylaxis and a number of lysosomal enzymes. These substances cause a local vascular and tissue reactions that cause allergic manifestation. XI. EOSINOPHILS Figure 20. Release of Histamine as an antigen attaches to IgE which is bound to Figure 18. Eosinophil. a mast cell. Constitutes about 2% of the total blood leukocytes. XIII. LEUKOPENIA Weak phagocytes, exhibits chemotaxis Doubtful to cause usual infection because they are weak phagocytes but exhibits chemotaxis Bone marrow produces very few WBCs Often produced in large numbers in people with parasitic infections This condition leaves the body unprotected against many bacteria and they migrate in large numbers into tissues diseases by parasites and other agents that might invade the tissues. They are produced in large numbers in people with parasitic Within 2 days after the bone marrow stops producing WBCs, ulcers infection. They kill parasites by: may appear in the mouth and colon. ○ Releasing hydrolytic enzymes (modified lysosomes) Bacteria from the ulcers rapidly invade surrounding tissues and the ○ Releasing highly reactive forms of oxygen that are blood. Without treatment, death often ensues in less than a week especially lethal to parasites (hydrogen peroxide) after acute total leukopenia begins. ○ Releasing highly larvicidal polypeptide called major basic Irradiation of the body by x-rays or gamma rays, or exposure to drugs protein (MBP) and chemicals that contain benzene or anthracene nuclei, is likely to Eosinophils also have a special propensity to collect in tissues in cause aplasia of the bone marrow. which allergic reactions Page 7 of 8 [PHYSIOLOGY] 1.07 RESISTANCE OF THE BODY TO INFECTION-LEUKOCYTES - Dr. Ma. Eileen Pascua Some drugs such as Chloramphenicol (an antibiotic), Thiouracil (used Consequently, the energy of the patient is greatly depleted, and to treat thyrotoxicosis) and even various barbiturate hypnotics on excessive utilization of amino acids by the leukemic cells causes rare occasions cause Leukopenia. especially rapid deterioration of the normal protein tissues of the Any decrease in the number of WBC immediately allows invasion of body. the adjacent tissue by the bacteria. Thus, while the leukemic tissues grow, other tissues become debilitated. After metabolic starvation has continued long enough, this factor alone is sufficient to cause death. XIV. LEUKEMIA Reference: Hall, J. E., & Guyton, A. C. (2016). Guyton and Hall Textbook of Medical Physiology. Elsevier. Figure 21. ALL and AML Leukemia as shown in a peripheral blood smear (PBS) A disease characterized by greatly increased numbers of WBCs in the circulating blood Uncontrolled production of WBCs can be caused by cancerous mutation of a myelogenous or lymphogenous cell. Cancer of the body’s blood forming tissue Caused by mutation in the DNA or can be precipitated by environmental factors ACUTE - cut off is 6 months CHRONIC - more than 6 months of occurrence TWO TYPES OF LEUKEMIA A. LYMPHOCYTIC LEUKEMIA (ACUTE LL or CHRONIC LL) caused by cancerous production of lymphoid cells, beginning in lymph nodes or other lymphocytic tissue and spreading to other areas of the body. affects the lymphoid cells/lymphocytes B. B. MYELOGENOUS LEUKEMIA (AML or CML) begins by cancerous production of young and myelogenous cells in the bone marrow and then spreads throughout the body so that WBCs are produced in many extramedullary tissues especially in the lymph nodes, spleen and liver. affects the myeloid cells that give rise to WBC and platelets EFFECTS OF LEUKEMIA The first effect of leukemia is metastatic growth of leukemic cells in abnormal areas of the body - leukemic cells from the bone marrow may invade the surrounding bone, causing pain and a tendency for bones to fracture easily. There’s development of infection, severe anemia, and bleeding tendency caused by thrombocytopenia. These effects result mainly from displacement of the normal bone marrow and lymphoid cells by the nonfunctional leukemic cells. Another important effect of leukemia on the body is excessive use of metabolic substrates by the growing cancerous cells The leukemic tissues reproduce new cells so rapidly that tremendous demands are on the body reserves for foodstuff, amino acids, and vitamins. Page 8 of 8