The Scope of Immunity PDF

The Scope of immunity Introduction to immunity Dr.Salma Mahmoud Alfadlabi Immunity (Resistance): Is the sum of naturally occurring defense mechanisms that protect humans from infectious diseases and other threats.  The Need for Self Recognition ▪ The human immune s...

The Scope of immunity Introduction to immunity Dr.Salma Mahmoud Alfadlabi Immunity (Resistance): Is the sum of naturally occurring defense mechanisms that protect humans from infectious diseases and other threats.  The Need for Self Recognition ▪ The human immune system—the defensive mechanisms that identify and neutralize these threats—is able to distinguish “nonself” organisms and molecules from “self,” that which belongs within the body.  Possible threats: ❑ Threats may enter the body from the outside (Exogenous): Infectious organisms or Toxic agents ❑ Arise from potentially: harmful changes occurring within the body (Endogenous): Opportunistic pathogens. Malignant transformation of a previously normal cell into a cancer cell.  Function of the immune system Prevent entry and growth of pathogens. Kill and eliminate pathogens and foreign bodies. Repair damage. The components of immune system: ❑ The first line of defense is provided by a set of mechanical, chemical, and biologic barriers that protect the body. Innate immune system. If these barriers are broken, ❑ The second line of protective systems is Innate immune system. ❑ The third line of protective systems is activated Adaptive immune system.  Types of immunity: There are two types of resistance mechanisms: ❑ Innate (nonspecific) natural. ❑ Adaptive(specific) Acquired. Note: any impairment of these defenses recurrent infections (opportunistic pathogens) Nonspecific immunity: ▪ Is innate. ▪ Not induced by exposure to infectious agents, although their numbers may increase in response to infection.* ▪ Do not exhibit specificity. (Single defense barrier affords protection against many different potential pathogens). * e.g: WBCs. Components of innate (natural) immunity: A- Mechanical barriers to infection: Contribute to innate immunity by inhibiting the attachment and penetration of infectious agents. I. Intact skin (Epidermis, sweating, phagocytic molecules and commensals microbes) and mucus membranes. The epithelium of mucous membranes lines all of the body's cavities that come into contact with the environment, such as the respiratory, gastrointestinal, and urogenital tracts II. Mucus. a. Movement of cilia of epithelial cells in the respiratory tract b. Coughing and sneezing. III. Shedding of cells that carry microbes. IV. The flushing action of saliva, tears, perspiration, urine and other body fluids. V. Vomiting, Peristalsis, diarrhea and other processes also eliminate pathogens. B- Chemical barriers to infection: ▪ Acid PH in most physiologic secretions.(skin, stomach and vagina) ▪ Lysozymes. ▪ Interferon. ▪ Antibodies and ▪ Complements: is a series of serum proteins that interact sequentially with one another to augment resistance. C- Physiologic factors contribute to innate immunity: ▪ The inflammatory process and phagocytosis is very important. ▪ Body temperature. ▪ Oxygen tension. ▪ Hormonal balance. ▪ Age.  C- Biological factors contribute to innate immunity: Commensal Microbes (not pathogenic ) except under special circumstances: ▪ Immunocompromised individuals. ▪ The introduction of medical devices, such as catheters. ▪ Any disruption of the normal flora of the body may lead to disease. Cells of the Innate Immune System: All blood-borne cells ultimately derive from pluripotent hematopoietic stem cells. White blood cells or leukocytes serve as defenders against infection by screening the tissues and organs of the body. They move around the body via the lymphatic and blood circulatory systems and can leave and reenter the circulation to move through body tissues.  Types of leukocytes: Pluripotent stems cells within the bone marrow give rise to all the cells found in the blood. Cells of the myeloid lineage differentiate further into platelets, erythrocytes, eosinophils, basophils (and mast cells), neutrophils, monocytes/macrophages and some dendritic cells. Cells of the lymphoid lineage differentiate further into T and B lymphocytes, NK cells, and some dendritic cells. I. Granulocytes: These cells have multilobed nuclei and cytoplasmic granules that contain amines (stained by basic dyes), basic proteins (stained with acidophilic or eosinophilic dyes). A. Neutrophils Comprising approximately 60% of the peripheral blood leukocytes, neutrophils are the most numerous leukocyte population. They are also called polymorphonuclear (PMN) cells because of their variable number of nuclear segments (two to five). B. Basophils and mast cells The acidic cytoplasmic granules of basophils contain vasoactive amines (e.g., histamine) that cause smooth muscle contraction. These bilobed cells are found in low numbers in the peripheral blood (0% to 1%) or in their tissue resident form, known as mast cells. Both basophils and mast cells are important in allergic reactions of the adaptive immune response.  C. Eosinophils So named because of their “eosin-loving” granules (eosin is a dye used in histology). Eosinophils are bilobed granulocytes. They comprise (0% to 5%) of the peripheral blood leukocytes. Eosinophils are active participants in innate and adaptive immune responses to parasitic helminth (worm) infections.  II. Agranulocytes: White blood cells that have unlobed nucleus and cytoplasm that contains few or no granules. derive from lymphoid or myeloid lineage precursors and account for approximately 35% to 38% of the leukocytes in circulation. A. Lymphoid lineage cells: Cells that differentiate along the lymphocytic pathways are known as lymphocytes. Lymphocytes may differentiate along one of several different pathways: (A) B lymphocytes or B cells reside in the bone marrow and are able to synthesize immunoglobulin molecules. In fact, B cells and their further differentiated progeny, plasma cells, are the only cells that are capable of immunoglobulin synthesis. (B) T lymphocytes (T cells) Other lymphoid lineage cells of bone marrow origin migrate to, differentiate within the environment of the thymus. Those cells (thymocytes) that exit the thymus are known as thymus-derived lymphocytes or T lymphocytes (T cells). Lymphocytes (C) Natural killer (NK) cell: These large, nonphagocytic, granular lymphocytes are named for their ability to kill abnormal (e.g., infected or malignant) host cells. They account for 5% to 10% of all lymphocytes in the circulation.  Monocytic lineage cells: I. Monocytes Mononuclear cells that differentiate from myeloid precursors are known as monocytes in the circulation or macrophages once they leave the circulation and enter the tissues. These cells are the scavengers of the body. They phagocytose, or pick up cellular debris, foreign cells, and particles and degrade them enzymatically. Monocytes Macrophages II. Dendritic cells Another group of phagocytic cells with both myeloid and lymphoid origins is collectively known as dendritic cells, so named for their branchlike cytoplasmic projections. Dendritic cells: Found throughout the body, but predominantly in potential portals of microbial entry (e.g., skin, lung, gastrointestinal tract). Like other phagocytes, dendritic cells actively engulf cells and particles in their environment by phagocytosis.  Case study: A 30-year-old female developed vaginal candidiasis (a fungal infection) after receiving antibiotic therapy for a sinus infection. One possible explanation for the fungal infection is antibiotic-induced reduction in vaginal……………. A. lysozyme secretion. B. mucus secretion. C. normal commensal bacteria. D. pH. E. RNases and DNases.