Adaptive Immune System 1) Leukocytes Flashcards
What do you lose in HIV?
T cells
Where do lymphocytes develop and where do they mature?
bone marrow, mature in thymus
What are the 2 types of T cells?
helper and killer
How does diversity arise in lymphocytes?
random re-arrangement of segmented antigen receptor genes during lymphocyte development
is antigen presenting required for small linear protein fragments?
Yes (not for intact macromolecules)
What are the immune system’s mechanism for displaying peptide antigens to T cells?
MHC molecules (also called HLA)
What do secondary lymphoid tissues act as a hub for?
lymphocyte activation
What capture opsonised antigens?
Follicular dentritic cells in lymphoid follicles
What transport antigens to lymph nodes?
migrating dendritic cells
What 2 signals are required for full activation of lymphocytes?
antigen receptor engagement
co-stimulatory signals
What are T cell dependent antigens?
protein antigens
co-stimulation provided by activated CD4+ helper T cells
What do activated T cells produce and express?
A cytokine (interleukin 2), and then express the IL2 receptor which drives mitosis and replication of the activated T cells
What do clonally expanded CD4+ cells differentiate into?
Helper T cells (Th cells)
What do Th cells secrete?
cytokines that affect the function of other immune cells
What does IL2 activate?
CD8+ T cells
What do IL4 and IL5 and IFNy activate?
B cells
What does IFNy also activate?
macrophages
How do Th cells help macrophages?
stimulate macrophage effector functions by hyperactivating them into much better killing machines:
Increased reactive oxygen species production
Increase inflammatory cytokine production
Increased expression of MHC molecules and co-stimulators such as B7
What does binding of the Th cell, IFNy and IFNy receptor on surface of a macrophage do?
stimualtes intracellular signalling events resulting in enhanced killing
What main 2 proteins do cytotoxic T cells employ to directly attack and destroy?
granzymes and perforin
What does perforin do?
form holes/pores in surface membrane of target cell allowing granzymes to enter
What do granzymes do?
induce target cells to undergo apoptosis
What do CTLs also secrete?
Fas ligand and Cytokines
How do Th cells help B cells?
Th cell secreted cytokines bind to B cells
Th cell surface molecules bind macrophage and B cell surface receptors
What B cell maturation events occur during response to T cell dependent antigens?
class switching somatic hypermutation
What are the 3 major helper T cell effector subtypes?
Th1, Th2 and Th17
What type of memory cells are there?
Memory Th cells
Memory CTLs
Memory B cells
