Lecture 11 - Lymphocytes Flashcards
Lymphocytes are central to
adaptive immune system and body defenses
Three major types of lymphocytes
- B cells
- T cells
- NL cells
B cells
responsible for antibody production
T cells
regulate adaptive immunity and are responsible for cell-mediated immune response
NK cells
play a role in innate immunity
Lymphocyte cell shape
small round cells
Lymphocytes nucleus
large, round, stains intensely with hematoxylin
What lymphocytes are bigger
NK larger than T or B cells
NK cells may contain obvious
cytoplasmic granules
Development of B vs T cells
B cells: Bone marrow, bursa, Peyer’s patches
T cells: thymus
Distribution of B vs T cells
B cells: lymph node cortex, splenic follicles
T cells: lymph node paracortex, splenic periarteriolar sheath
Antigen receptors of B vs T cells
B cells: BCR- immunoglobulin
T cells: TCR- protein heterodimer associated with CD3, CD4, CD8
Important surface antigens of B vs T cells
B cells: immunoglobulin
T cells: CD2, CD3, CD4, CD8
Antigens recognized of B vs T cells
B cells: free foreign proteins
T cells: processed foreign proeins in MHC
Progeny cells of B vs T cells
B cells: plasma cells, memory cells
T cells: effector T cells, memory T cells
Secreted products of B vs T cells
B cells: immunoglobulins
T cells: cytokines
Stages in life history of lymphocytes
Naive cell->antigen recgonition->activated or effector lymphocyte->proliferation->differentiation->memory lymphocyte
4 key antigen receptors of immune system
TCR, MHC I, MHC II, BCR
T cell antigen receptor categories
a/B or y/g
a/B T cell accessory molecules
CD4 and CD8
CD4 functional subdivision
Helper/Regulatory and memory
CD8 functional subdivisions
cytotoxic/regulatory and memory
T cell antigen receptors
aB and yg
T cell surface receptors
CD4 and CD8
aB T cells
- CD4+ aB T cells
- CD8+ aB T cells
T helper cells or CD4+ aB T cells recognize
antigen on MHC II
type of T helper cell is defined by
cytokines secreted not by surface molecule
Naive TH cells are called
TH0 cells
TH0 cells differentiate into
TH1, TH2, TH17, Treg
TH0 cell differentiation depends on
signals TH0 cells receive from APCs and the local environment
TH1 cells secrete
IFNy, IL-2
TH1 cells are important in protection against
some intracellular (viral, Mycobaterium, Salmonella, Listeria, Brucella) and extracellular pathogens
TH1 cells secrete cytokines that activate
macrophages, meutrophils, NK cells, and CTLs to be better killers
TH1 cells secrete cytokines that signal
B cells to make opsonizing and complement fixing antibodies for extracellular bacteria or certain viruses
TH2 cells secrete
IL-4, IL-5, IL-9, IL-13
TH2 activate
mast cells and eosinophils, and B cells to make IgE
TH2 cells provide defense against
some parasites and some mucosal pathogens
TH2cells are important in
IgE mediated allergies
TH17 cells secrete
IL-17, IL-21, IL-22
Th17 attract and activate
neutrophils and monocyte, leading to acute inflammation
TH17 cells important in
response to extracellular bacteria and fungi
Treg cells secrete
IL-10, IL-35, TGFB
Treg supress
T cell response by secreting suppresive cytokines
Treg help prevent
reactions to self-peptides
If naive T cell recognizes antigen without any danger signals, it may become
Treg
In most cases a self antigen would be encountered in the absence of ______. These self-reactive T cells are then induced to become _____ and do not induce an immune response to the self-antigen but ____
inflammation; Treg, prevent it
Another name for cytotoxic T lymphocytes
CTLs/CD8 T cells
CD* aB t cells recognize antigen on
MHC I
What do CD8+ aB T cells do once they encounter antigen
clonally expand, differentiate and develop a killing machinery in their cytoplasm, kill cell that has antigen it recognizes bound to an MHC I molecule
CD8+ aB T cells
important in protection from intracellular microbes that cause the synthesis of foreign proteins in the cytoplasm, such as viruses
yG T cells defined by their
TCR
yG T cells recognize
intact, unprocessed antigens; also recognize cell surface ‘stress’ proteins, (recognize protein and non-protein antigens)
yG T cells important at
mucosal surfaces, many are intraepithelial lymphocytes
yG T cells are not as well understood as
aB T cells
B cells antigen recognition
intact, unprocessed molecules
B cells response to antigen
plasma cells produce antibodies
CD4+ TH1 antigen recognition
Exogenous peptides, processed and presented in MHC II
CD4+ TH2 antigen recognition
exogenous peptides, processed and presented on MHC II
CD4+ Treg antigen recognition
self-peptides on MHC II
CD8+ T cytotoxic cells (CTL) antigen recognition
endogenous peptides, processed and presented on MHC I
yG T cells antigen recognition
intact, unprocessed antigens, also ‘stress proteins’
CD4+ TH1 response to antigen
Secrete cytokines which activate phagocytes, NK, CTLs to fight intravesicular pathogens, influence B cells to make antibody for extracellular pathogens
CD4+ TH2 response to antigen
Secrete cytokines which help antibody production, especially IgE, to fight parasites and cause allergies
CD4+ TH17 response to antigen
Secrete cytokines that stimulate production of neutrophil chemokines by cells at the site of infection
CD4+ T reg response to antigen
Secrete suppressive cytokines or suppress T cell responses by cell-cell contact
CD8+ T cytotoxic cells (CTL) response to antigen
Cytotoxic for cell synthesizing foreign proteins
yG T cells response to antigen
Secrete cytokines and/or cytotoxic for cells with abnormal surface antigens, stress markers, heat shock proteins
NK cells are NOT ___ and have NO ____
- antigen specific
- surface immunoglobulin (CD3, CD4, CD8)
NK cells activated by
IFNy, TNF, IL-2
NK cells cytotoxic for cells that
do not express normal MHC I molecules with normal peptides, or cells that express stress proteins
3 major receptors of NK cells
- Ly49
- NKG2D
- CD16
Lymphocytes all look the same byt can be differentiated by
characterisitic cell surface molecules
cell surface molecules are classified by the
CD (cluster of differentiation) system