Interaction with Innate Immunity
Adaptive immune responses closely interact with innate immune responses. |
Host is considered immune compromised if any part of the innate or adaptive system is impaired. |
Adaptive responses come into action when innate defenses fail. |
Four Main Stages of Adaptive Immune Responses
Antigen Presentation: Involves antigen-presenting cells (APCs) showing antigens to T cells. |
Lymphocyte Activation: Lymphocytes are activated by cytokines |
Lymphocyte Proliferation and Differentiation: Leads to effector cells and memory cells. |
Antigen Elimination and Memory: Cellular and humoral responses collaborate to eliminate the antigen. |
T Cell Differentiation
T cells can be classified into T cytotoxic cells (TC cells) and T helper cells (TH cells) |
T helper cells, especially CD4+ T cells, release cytokines and activate other immune cells. |
T helper cells can further differentiate into subclasses like TH1, TH2, and Treg cells |
MHC I and MHC II in Antigen Presentation
MHC I presents intracellular antigens on most body cells. |
MHC II, exclusive to APCs, presents extracellular antigens to T cells |
MHC matching is crucial for tissue transplantation (allorecognition). |
Active vs. Passive Immunity
Active immunity involves memory cell and antibody formation, obtained through infection or vaccines. |
Passive immunity entails receiving antibodies without memory cell involvement, providing temporary protection. |
Naturally acquired active and artificially acquired active immunity confer long-lasting protection, while naturally acquired passive immunity provides only temporary protection. |
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Characteristics of Adaptive Immune Responses
Take longer to mount (days to weeks) compared to innate responses. |
Specific to a particular antigen and exhibit immunological memory. |
Secondary exposure to the same antigen results in a rapid and effective response. |
Production and Function of B and T Cells
B and T cells recognize a wide range of antigens |
T cells originate in the bone marrow, mature in the thymus, and play roles in both cellular and humoral branches. |
B cells coordinate the humoral response by producing antibodies |
Mature B and T cells mainly reside in lymphoid tissues. |
T Cytotoxic Cells
CD8+ T cytotoxic cells directly destroy infected or cancerous cells. |
Roles in antigen elimination involve interferons, MHC I production enhancement, and inducing apoptosis in target cells. |
Antibodies in Antigen Elimination
Plasma cells secrete antibodies (immunoglobulins) that neutralize antigens, activate complement cascades, and promote phagocytosis. |
Different antibody isotypes (IgG, IgA, IgM, IgE, IgD) have specialized functions |
MHC Matching in Transplantation
Critical for avoiding tissue rejection in transplantation. |
Allorecognition is the process by which lymphocytes distinguish self from foreign MHCs. |
Transplant waiting lists exist due to the difficulty of finding an adequate MHC match. |
MHC Matching in Transplantation
Critical for avoiding tissue rejection in transplantation. |
Allorecognition is the process by which lymphocytes distinguish self from foreign MHCs. |
Transplant waiting lists exist due to the difficulty of finding an adequate MHC match. |
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Branches of Adaptive Immune System
Cellular response (T cell-mediated immunity). |
Humoral response (antibody-mediated immunity). |
Both aim to eliminate identified antigens and form memory for faster future responses. |
Antigens and Immunogenicity
Antigens trigger immune responses and can be proteins, polysaccharides, or molecules in various organisms. |
Immunogenicity depends on antigen size, molecular complexity, and chemical composition |
Stages of Cellular/ Humoral Immune Responses
Both branches progress through four stages: antigen presentation, lymphocyte activation, lymphocyte proliferation and differentiation, antigen elimination, and memory. |
Memory Cells in Immune Response
Effector cells die off, while memory cells provide long-lasting immunological memory. |
Enable rapid reactivation of the adaptive response upon encountering the same antigen. |
Secondary immune response involves quick generation of high-affinity IgG antibodies |
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