Adapative Immunity Flashcards
(18 cards)
What is the main characteristic that distinguishes adaptive immunity from innate immunity?
Adaptive immunity is slow, specific, and potent, with immunological memory.
Which cells are responsible for adaptive immune responses?
B cells and T cells.
What is the function of Major Histocompatibility Complex (MHC) molecules in adaptive immunity?
MHC molecules present antigens to T cells. MHC I (on all nucleated cells) presents intracellular antigens to CD8+ cytotoxic T cells. MHC II (on APCs) presents extracellular antigens to CD4+ helper T cells.
Where do B cells develop and mature?
B cells develop and mature in the bone marrow.
Where do T cells develop and mature?
T cells develop in the bone marrow but mature in the thymus.
How does the immune system generate over 10⁷ different antigen-binding receptors despite the limited size of the genome?
Through somatic DNA recombination (gene rearrangement).
What are the two types of selection that antigen receptors undergo, and what is their purpose?
Positive selection ensures T cells weakly recognize self-antigens and bind MHC. Negative selection eliminates T cells that strongly recognize self-antigens to prevent autoimmunity.
What are the primary and secondary lymphoid tissues, and what is their role in adaptive immunity?
Primary: Bone marrow (B cell maturation) and thymus (T cell maturation). Secondary: Lymph nodes, spleen, MALT, where naive B/T cells encounter antigens and activate.
What is the main function of B cells in adaptive immunity?
B cells differentiate into plasma cells to secrete antibodies and act as APCs to present antigens to T helper cells.
Where do B cells proliferate and undergo class switching?
In the germinal centers of secondary lymphoid tissues (lymph nodes, spleen).
How do B cells get activated?
- Thymus-Independent (TI) Activation
- BCR binds directly to microbial components (e.g., polysaccharides on bacterial walls).
- Does NOT require T helper cells (T cell-independent).
- Leads to a rapid but less diverse antibody response.
- Thymus-Dependent (TD) Activation
- BCR binds to a protein antigen, but requires T follicular helper (TFH) cells.
- TFH cells secrete cytokines (IL-6, IL-4, IFN-γ, TGF-β) that guide antibody production and class switching.
- Leads to a stronger and more diverse antibody response.
What are the five classes of antibodies, and what are their functions?
IgG (long-term immunity, opsonization, crosses placenta), IgA (mucosal immunity, secretions), IgM (first response, complement activation), IgE (allergy, parasite defense), IgD (B cell activation).
What are the three main functions of antibodies in eliminating pathogens?
1) Neutralization - blocks pathogen entry. 2) Opsonization - coats pathogen for phagocytosis. 3) Complement Activation - triggers MAC for lysis.
What are the two main types of T cells, and what MHC molecules do they recognize?
CD8+ Cytotoxic T cells recognize MHC I (on all nucleated cells) and kill infected cells. CD4+ Helper T cells recognize MHC II (on APCs) and activate other immune cells.
What are the four major subsets of CD4+ T helper (TH) cells, and what are their primary functions?
TH1 (IFN-γ, enhances macrophage killing, intracellular pathogens), TH2 (IgE, parasite defense), TH17 (IL-17, recruits neutrophils, extracellular bacteria/fungi), TFH (B cell activation, antibody production).
What is the function of regulatory T cells (Tregs)?
Tregs suppress immune responses to prevent excessive activation and autoimmunity.
What is immunological memory, and how does it improve immune responses?
- Immunological memory is the ability of the adaptive immune system to respond more rapidly and effectively upon repeat exposure to the same antigen.
- It is created by memory B and T cells, which allow for faster, stronger, and more specific responses compared to the first encounter.
- Memory B cells → Respond up to 100x faster and produce higher-affinity antibodies upon re-exposure.
- Memory T cells → Rapidly recognize previously encountered antigens and trigger a stronger, faster immune response.
What are the three types of memory T cells, and how do they differ?
Tcm (circulate in blood/lymphoid tissues, long-term response), Tem (circulate in blood/peripheral tissues, rapid cytokine secretion), Trm (permanently in tissues, localized immunity).
