Immuno 2 Flashcards
(19 cards)
What is the primary route by which foreign antigens enter the body?
Through the skin, respiratory tract, or gastrointestinal tract. They are captured by APCs and transported to peripheral lymphoid tissues where adaptive immune responses are initiated.
What are the main types of antigen-presenting cells (APCs)?
Macrophages, dendritic cells, and Langerhans cells. Dendritic cells are the most efficient.
What changes occur during dendritic cell maturation?
Increased expression of MHC II and chemokine receptors, making them responsive to cytokines and capable of T cell activation.
What are the 4 main subfamilies of chemokines
CXC, CC, CX3C, and XC. These proteins interact with G protein-coupled receptors (chemokine receptors) on target cells.
What is the major function of the MHC complex?
Cell surface protein. Binds antigens from pathogens and display them on cell surfaces for recognition by T cells. It also determines organ transplant compatibility and autoimmune disease susceptibility.
What are the differences between MHC class I and II molecules?
MHC I is found on all cells (excludes RBC and also neurons), presents endogenous antigens
8-10 aa long antigens, and activates CD8 T cells.
MHC II is on APCs, presents exogenous antigens
12-18 aa long
and activates CD4 T cells.
What defines whether a T cell will trigger a cytotoxic or helper response?
CD8 T cells interact with MHC I and respond to endogenous antigens. TCR and cell activation leads to killing of infected cells and activation of CD4
CD4 T cells interact with MHC II and respond to exogenous antigens. TCR and cell activation leads to activation of B cells
What are naive vs effector T cells?
Naive T cells have not encountered antigen. Effector T cells have been activated, proliferate, and are ready to perform immune functions like cytotoxicity or cytokine release.
What molecules are required for full T cell activation?
TCR-MHC interaction
LFA1-ICAM1 adhesion molecules
CD28 B7-1 and B7-2 costimulation.
What happens to CD28 after stimulation
Becomes CTLA-4 inhibits further reactivity
What is the role of Th1, Th2, and Th17 CD4+ T cell subsets?
Th1: cell-mediated immunity and intracellular pathogens. Th2: antibody production and extracellular parasites. Th17: neutrophil recruitment for extracellular bacteria.
What markers differentiate effector and memory T cells?
Effector T cells express CD69, while memory T cells express CD45RA.
What is the role of B cells in adaptive immunity?
B cells recognize antigens, present them via MHC II, and produce antibodies after activation by CD4+ T cells.
How do B and T cells interact?
B cells present antigens on MHC II to CD4+ T cells in lymph nodes, requiring TCR and CD40/CD40L binding to activate B cells into plasma cells.
What are thymus-dependent and thymus-independent B cell responses?
Thymus-dependent requires T cell help and antigen delivery to B cell follicles
Thymus-independent involves TLRs and polysaccharides that cross link B cell receptors and results in short-lived IgM-producing plasma cells.
What influences class switch recombination in B cells?
Cytokines from T cells, such as IL-4 (IgE), TGF-beta (IgA), and IFN-gamma (IgG).
What signals are needed for CD8+ T cell activation?
Recognition of antigen on MHC I and CD28-B7 costimulation. Proliferation requires IL-2.
How do CD8+ cytotoxic T cells kill infected cells?
By releasing perforin to form membrane pores and granzymes that enter and trigger apoptosis in the target cell.
What happens after a primary immune response?
90% of cells die, 10% become memory B and T cells. Upon re-exposure, memory responses are faster and stronger. Secondary immune response peaks within 4 days
