Immune System Cells PDF

# Sistema Inmunitario - Mechanism of complex and potent defense - **Primary Function**: Defend the body against pathogens - **Primary Organs**: Bone marrow and thymus - **Secondary Organs**: Lymph nodes, lymph, and spleen ## How the immune system reacts The immune system reacts in **2 ways**:...

# Sistema Inmunitario - Mechanism of complex and potent defense - **Primary Function**: Defend the body against pathogens - **Primary Organs**: Bone marrow and thymus - **Secondary Organs**: Lymph nodes, lymph, and spleen ## How the immune system reacts The immune system reacts in **2 ways**: ### Innate Response - Faster reaction. - Recognizes molecules found in pathogens. - Causes inflammation. ### Adaptive Response - Slower reaction, but with higher specificity. - Involves two types of cells: - **T cells**: Kill pathogens and infected cells. - **B cells**: Produce antibodies. ## Cells of the Immune Response - Derived from hematpoietic stem cells (bone marrow). - Developed in either the myeloid or lymphoid series. ### Myeloid Series: - **Erythroblasts and Megakaryocytes**: Do not participate in immune reactions - **Eosinophils and Mastocytes**: Mostly involved in allergic reactions. - **Red Blood Cells**: Transport oxygen and convert carbon dioxide. - **Platelets:** Involved in blood clotting and inflammation. - **Neutrophils**: Essential phagocytes of the blood; kill bacteria. - **Basophils**: Function in inflammatory and allergic situations. - **Eosinophils**: Act against worms and fungi; involved in allergic and inflammatory reactions. - **Mast Cells**: Tissue cells that give rise to local inflammatory reactions; are involved in allergy symptoms. - **Monocytes**: Blood phagocytes which leave the circulation and become macrophages and dendritic cells. - **Macrophages**: Large phagocytes that devour and eliminate foreign cells. - **Dendritic Cells**: Process foreign material and present it to lymphocytes. ### Lymphoid Series - Lymphocytes mature in the thymus, spleen, and lymph nodes. - **T lymphocytes**: Mature in the thymus. - **B lymphocytes**: Mature in the bone marrow. - **T cells**: Recognize cells infected by pathogens. - **B cells**: Produce antibodies that target pathogens. - **T cells**: Activated B cells, which produces antibodies. - **Null cells**: Kill abnormal cells by cell-mediated immunity. ## Cells of the Infectious Response - Groups of cells that are more likely to be infected: - **Granulocytes**: Neutrophils, Basophils, Eosinophils - **Agranulocytes**: Monocytes, Lymphocytes, Macrophages ## Innate Response - Protects against microorganisms. - **First Line of Defense**: - Anatomic barriers - Cellular response - Chemical response - **Adaptive Response**: - Second line of defense ## Innate Immune Response - The immune system you are born with. - It creates resistance to the progression of a pathogen. Components: - Physical barriers (skin and native flora) - Cough reflex - Enzymes in tears and skin oils - Mucus - Gastric acid - Chemical immunity ## Skin and Mucous Membranes - Thick layers of skin contain insoluble keratins. - The digestive and urogenital tracts contain: - **Peptidoglycan**: A unique component of the bacterial cell wall. - **Lysozyme**: An enzyme concentrated in tears and conjunctiva. ## Factors that Promote Colonization - Low pH of the vagina and stomach. - Difficulty of colonization. - Small particles (5 to 10µM). - Skin and mucous contain concentrations of lymphoid tissue. - Lipoid aggregations trap and deliver invaders to phagocytic cells. ## Organs and Tissues - **Skin:** Contains oils and acidic pH. - **Mouth and GI tract:** Contains enzymes. - **Stomach:** Low pH. - **Small Intestines:** Digestive enzymes. - **Large Intestine:** Normal flora shares intestinal flora. ## The Gut - In the intestine, cells that are normally present (B cells) are enveloped in a mucus layer that contains macrophages. - *Shigella*, a pathogen, takes advantage of the receptivity of M cells. - M cells attack enterocytes (intestinal cells). ## Monocytes: Anti-Infectious Actions - **Morphological Terms**: Cells that differentiate rapidly. - **Macrophages**: Found circulating in the blood and in tissues. - Macrophages contain surface receptors such as mannose and fructose and LPS (lipopolysaccharide). ## Dendritic Cells: Anti-Infectious Actions - Reside in the skin. - Contain phagosomes and respond to alien antigens. - PAMPs (pathogen-associated molecular patterns) are recognized and phagocytosis occurs, resulting in the release of cytokines. - Dentritic cells migrate to lymphoid tissues. ## Granulocytes: Anti-Infectious Actions - Neutophils are the most active polymorphonuclear cells (PMNs). - PMNs contain multilobed nuclei and granules that contain enzymes such as: - Peroxidase - Lysozyme - Defensins - Collagenase ## Granulocyte Actions - Granulocytes exhibit both independent and dependent pathways. - Present in circulation. - Involved in allergic reactions, along with mast cells and basophils. - Defend against parasitic infections. - Thought to damage parasitic membranes. ## Basophils - 1% of leukocytes, white blood cells. - Release histamine, which causes dilation and swelling. ## Phagocytosis - The most important defense against microbial invaders. - Phagocytosis is carried out by macrophages, dendritic cells, and neutrophils. - Phagocytosis involves recognizing a pathogen (pathogen-associated molecular patterns), neutralization, agglutination and oposonization. - **Opsonization**: Opsonization involves the use of lectins (e.g., carbohydrates), formation of RGD motifs (e.g., arginine, glycine, aspartic acid) and other pathways. - Receptors (TLR, toll-like receptors) recognize specific motifs: such as a bacterial molecular pattern contained in peptidoglycan. - Atrapped organisms eventually end up in the interior of the phagocyte. - Organisms are encapsulated by the phagocyte's membrane.