Immunity Flashcards
What are the key features of the innate immune system?
Present and active from birth.
Fast response (minutes to hours).
Non-specific, with no immunological memory.
Multi-layered: physical barriers, proteins, and immune cells.
Name the three pathways of complement activation and their triggers.
Alternative Pathway: Spontaneously active at low levels.
Mannose Binding Lectin (MBL) Pathway: Triggered by mannose on pathogen surfaces.
Classical Pathway: Triggered by antibodies (IgG or IgM) bound to pathogens.
What are the three main outcomes of complement activation?
Membrane Attack Complex (MAC): Punches holes in pathogens.
Opsonization: Pathogens are coated with C3b to enhance phagocytosis.
Chemoattraction: C3a and C5a attract phagocytes to the infection site.
What is the function of macrophages in innate immunity?
Phagocytose pathogens and debris.
Produce cytokines (e.g., IL-1β, TNF-α) to recruit other immune cells.
Clear dead cells and stimulate inflammation.
How do neutrophils combat infection?
Phagocytose pathogens.
Release granules and NETs (neutrophil extracellular traps).
Undergo respiratory bursts, producing reactive oxygen species.
What is antigen processing?
The breakdown of proteins into peptides that are displayed on MHC molecules for T cell recognition.
What are the key differences between MHC Class I and MHC Class II?
MHC Class I: Presents intracellular antigens to CD8+ cytotoxic T cells. Expressed on all nucleated cells.
MHC Class II: Presents extracellular antigens to CD4+ helper T cells. Expressed only on professional antigen-presenting cells (APCs).
Describe the endogenous pathway of antigen presentation
Cytosolic proteins are degraded by the proteasome.
Peptides are transported to the ER by TAP.
Peptides are loaded onto MHC Class I and transported to the cell surface.
Describe the exogenous pathway of antigen presentation.
Proteins are endocytosed and degraded in phagolysosomes.
Peptides are loaded onto MHC Class II after fusion with a vesicle.
Peptide-MHC Class II complexes are displayed on the cell sur
How do B cells develop in the bone marrow?
Progenitors interact with stromal cells via VCAM-1 and SCF.
IL-7 supports late-stage development.
B cells undergo somatic recombination of BCR genes for diversity.
What is the role of B cell receptors (BCRs)?
Each BCR is unique and recognizes a specific antigen.
Composed of two heavy chains and two light chains.
What happens during B cell activation?
B cells bind their cognate antigen, leading to BCR clustering.
Activated B cells differentiate into plasma cells, producing antibodies.
Describe the structure and function of antibody isotypes.
Describe the structure and function of antibody isotypes.
How are T cells developed and educated?
Born in the bone marrow, educated in the thymus.
Undergo positive selection (bind self-MHC) and negative selection (eliminate self-reactive T cells).
What are the roles of CD4+ and CD8+ T cells?
CD4+ Helper T Cells: Coordinate immune responses (TH1 activates macrophages, TH2 supports B cells).
CD8+ Cytotoxic T Cells: Kill virally infected or cancerous cells via perforin and granzyme.
What is the function of dendritic cells (DCs) in T cell activation?
Capture antigens, migrate to lymph nodes, and present them to T cells via MHC Class I and II.
Activate naïve T cells, leading to proliferation and differentiation.
Describe the structure of the T cell receptor (TCR).
Composed of variable (V) and constant (C) regions.
Recognizes peptide antigens presented on MHC molecules.
How does IL-2 contribute to T cell activation?
IL-2 drives rapid proliferation of activated T cells.
Effector T cells differentiate and leave lymph nodes to respond to infections.
