Antibody and Cell-Mediated Effector Functions Flashcards
What are the antibody-mediated effector functions?
Antibodies neutralize pathogens, opsonize them for phagocytosis, and activate the complement system.
What is neutralization by antibodies?
Antibodies bind to pathogens or toxins, blocking their ability to infect cells or cause damage.
What is opsonization?
Antibodies coat pathogens, making them easier for phagocytes to recognize and engulf.
How do antibodies activate the complement system?
Antibodies (mainly IgM and IgG) bind to antigens, activating the complement cascade, leading to pathogen lysis.
What is antibody-dependent cell-mediated cytotoxicity (ADCC)?
Antibodies bound to target cells recruit NK cells, which kill the antibody-coated cells.
What are Fc receptors?
Receptors on immune cells (e.g., macrophages, neutrophils, NK cells) that bind the Fc region of antibodies, triggering effector functions like phagocytosis and cytotoxicity.
What are IgM antibodies?
The first antibodies produced during an immune response, effective at activating complement and neutralizing pathogens.
What are IgG antibodies?
Provide long-term immunity, are involved in neutralization, opsonization, and complement activation.
What are IgA antibodies?
Found in mucosal areas, they protect against pathogens at mucosal surfaces by preventing their attachment.
What are IgE antibodies?
Involved in allergic responses and defense against parasitic infections by binding to allergens and activating mast cells.
What is cell-mediated immunity?
Involves T cells that directly kill infected cells or help other immune cells to respond to pathogens.
What are cytotoxic T cells (CD8+ T cells)?
Kill infected or cancerous cells by recognizing antigens presented on MHC Class I molecules.
What are helper T cells (CD4+ T cells)?
Activate other immune cells, such as cytotoxic T cells, macrophages, and B cells, by releasing cytokines.
What is a T-cell receptor (TCR)?
On T cells, recognizes processed antigens presented on MHC molecules, triggering immune responses.
What are MHC Class I molecules?
Present endogenous antigens to CD8+ T cells, which kill infected cells.
What are MHC Class II molecules?
Present exogenous antigens to CD4+ T cells, which help activate other immune cells.
What is T-cell activation?
Occurs when a TCR binds to an antigen-MHC complex, with co-stimulatory signals needed for full activation.
What is clonal expansion of T cells?
Activated T cells proliferate, producing effector T cells that combat the antigen and memory T cells for faster future responses.
What is T-cell memory?
Memory T cells persist long-term and provide rapid responses upon re-exposure to the same antigen.
What are cytotoxic T cell effector functions?
Release perforin and granzymes to induce apoptosis in infected or cancerous cells.
What is perforin?
A protein released by cytotoxic T cells that forms pores in target cell membranes, allowing granzymes to enter.
What are granzymes?
Enzymes released by cytotoxic T cells that trigger apoptosis in target cells.
What is the Fas-FasL interaction?
FasL on cytotoxic T cells binds to Fas on target cells, triggering apoptosis via the extrinsic pathway.
What are T helper 1 (Th1) cells?
Activate macrophages and cytotoxic T cells to fight intracellular pathogens like viruses and bacteria.
What are T helper 2 (Th2) cells?
Stimulate B cells to produce antibodies, especially effective against extracellular pathogens.
What are T helper 17 (Th17) cells?
Promote inflammation and recruit neutrophils to fight fungal infections and some bacterial infections.
What are T follicular helper (Tfh) cells?
Assist B cells in germinal centers to produce high-affinity antibodies and form memory B cells.
What are regulatory T cells (Tregs)?
Suppress immune responses to maintain self-tolerance and prevent autoimmune reactions.
What is the role of macrophages in cell-mediated immunity?
Activated by Th1 cells, macrophages increase phagocytosis and pathogen destruction.
What are granulocytes in immunity?
Neutrophils, eosinophils, and basophils contribute to defense through phagocytosis, degranulation, and inflammation.
What is the role of NK cells in immunity?
Natural killer cells recognize and kill cells infected with viruses or transformed by cancer, even without antigen-specific receptors.
What is an immune synapse?
The contact site between a T cell and its target cell, where antigen recognition and signaling take place.
What are lymphokine-activated killer (LAK) cells?
NK cells or cytotoxic T cells activated by cytokines to enhance their killing ability.
What is antibody isotype switching?
B cells can switch from producing IgM to IgG, IgA, or IgE in response to different pathogens or cytokine signals.
What is humoral immunity?
Mediated by antibodies produced by plasma cells, it targets extracellular pathogens and toxins.
What is immunotherapy targeting T cells?
Includes strategies like checkpoint inhibitors or CAR-T cell therapy to enhance T-cell responses against tumors.
What is tumor immunity?
Cytotoxic T cells and NK cells recognize and kill tumor cells displaying abnormal antigens on MHC molecules.
How do pathogens evade the immune system?
Pathogens can evade immune detection by altering their antigenic profile or inhibiting T-cell activation.
