Adaptive Immunity
Introduction:
1. Definition: Specific defense mechanism against infectious organisms.
2. Trigger: Occurs when innate immune mechanisms fail to eliminate infectious organisms.
# II. Adaptive Immune Response
1. Generation of: Antigen-specific lymphocytes (effector cells) and memory cells.
2. Function: Prevents reinfection with the same organism.
1. Acquired /specific Immunity: Another name for adaptive immunity.
2. Specific Immunity: Targets specific infectious organisms.
1. Humoral Immunity: Defense against extracellular microbes.
2. Cell-Mediated Immunity: Defense against intracellular microbes.
3. Memory: Important aspect of specific immunity.
# II. Humoral Immunity
1. Mediated by: Antibodies produced by B lymphocytes.
2. Function: Neutralize and eliminate extracellular microbes and toxins.
3. Limitation: Cannot access microbes inside infected cells.
How Antibodies Work
1. Secretion: Antibodies enter circulation and mucosal fluids.
2. Action: Stop microbes at mucosal surfaces and in blood.
.Cell-Mediated Immunity (CMI)
1. Definition: Responses mediated by lymphocytes (T cells).
2. Memory factor: Important for secondary immune response.
3. Secondary response: Faster, stronger, and more effective.
# II. Lymphocytes
1. Two types: T cells (thymus-derived) and B cells (bone marrow-derived).
2. T cells: Mediate CMI, recognize protein antigens.
3. B cells: Produce antibodies, recognize various molecules.
# III. Lymphoid Organs in Fish
1. Primary organs: Thymus and kidney.
2. Kidney: Functions as bone marrow equivalent.
3. Secondary organs: Spleen and gut-associated lymphoid tissue (GALT).
# IV. Functions of T Cells
1. Activate phagocytes: Destroy microbes in intracellular vesicles.
2. Kill infected cells: Eliminate host cells harboring microbes.
# V. Antigen Recognition
1. T cells: Recognize protein antigens.
2. B cells and antibodies: Recognize various molecules (proteins, carbs, nucleic acids, lipids).
Immunological Memory
1. Definition: Ability of specific immune system to remember past infections.
2. Result: Faster and stronger immune response upon re-exposure.
# II. Formation of Immunological Memory
1. First encounter: Antigen produces short-lived effector cells (Activated Th cells, Plasma cells, Cytotoxic cells).
2. Long-lived memory cells: Formed from non-primed lymphocytes.
# III. Characteristics of Immunological Memory
1. Rapid response: Memory cells quickly respond to re-exposure.
2. Stronger response: Larger and more effective responses to repeated exposures.
# IV. Importance of Immunological Memory
1. Adaptive immunity: Essential feature of adaptive immune responses.
2. Protection: Ensures protection against repeated infections.
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