Immunology 4 Flashcards
(23 cards)
describe the production of effector cells in adaptive immunity
the naive lymphocytes encounter their antigen, help from CD4+ T cells induces proliferation and differentiation into effector and memory cells
how are the hypervariable regions of BCRs and TCRs so variable?
because they can rearrange the V D and J genes, along with mutation
what is clonal deletion?
when a T or B cell recognises self and it programmed to die
what is clonal selection?
when a T cell binds properly to MHC in the thymus and it sent to do clonal expansion: gives rise to many lymphocytes which express the same TCR as the original
what are the four postulates of clonal selection?
- each lymphocyte expresses one unique TCR/BCR type
- binding of antigen to TCR/BCR causes activation
- Activation leads to differentiation and proloferation of cells with same receptor as original cell
- Lymphocytes recognising self are deleted in early development
where does T cell activation happen?
in the lymph nodes
what is the primary response for T cell activation?
first time the T cell encounters cognate antigen loaded on MHC
- differentiation and proliferation of naiive T cells into effector T cells
each T cell has ______ type(s) of TCR that is/are specific for _______ epitope(s)
each T cell has a single type of TCR that is specific for a single epitope
describe the requirements of the MHC in MHC restriction
must recognise the peptide and be specific for the TCR
describe the structure of the TCR complex
TCR complex = TCR + CD3 complex
CD4/CD8 coreceptors bind to distinct MHC region and amplifies the signal from CD3 and stabilises the MHC
what is the role of CD3?
intracellular signalling involved in T cell activation
what is signal 2 in primary activation?
costimulatory molecules expressed by APC promote survival and proliferation
-> CD80/86 on APC binds CD28 on T cell
what is signal 3 in primary activation?
cytokine secretion to induce T cell differentiation
true or false, both CD4+ and CD8+ T cells proliferate and differentiate into effector and memory cells
true
secondary response to an antigen only has which signal?
signal 1
describe the mechanism of action of CTLA4
it is upregulated in T cells to attenuate/decrease the co-stimulation of T cells by binding to CD28
- immune checkpoint
what does PDL1 do?
cancer cell expresses PDL1 ligand which binds to PD1 on T cells and prevents their activation (linked Q)
how can we use immunotherapy to resolve PDL1-PD1 issue?
since we know that PDL1-PD1 prevents T cell activation, we can target antibodies to bind to those molecules and prevent then from binding, and T cell will be activated and attack
how do cytotoxic T cells kill
perforin and granzyme
how are NK and CTLs different?
NK cells kill in a non-antigen specific manner, while CTLs have to recognise MHC I and then kill
how does perforin and granzyme work?
perforins form pores in target cell membrane, and granzyme induces endocytosis for perforin to act internally
why are CD4+ T cells helper cells?
they secrete cytokines to induce proliferation and activation of other immune system cells
what impact do cytokines have of CD4+ T cell differentiation and proliferation?
different types of cytokines exposed to CD4+ cell means different subsets of helper T cell produced
