Express BCR with which they can capture free antigen to display to B cells

Present antigen to T cells within the germinal centre which provide ongoing B cell help

Endocytose antigen for processing and presentation on surface MHC molecules

Can display antibody bound antigen via surface Fc receptors

Migration to lymph nodes

Antigen presentation

The phosphorylation of ITAMS

The expression of the same set of cytokines

Lck binds to CD4 and leads to phosphorylation of ITAM

Lck binds to CD3 to induce direct signalling through the TCR

Lck binds to the ITAMs and leads to phosphorylation

Lck binds to the TCR cytoplasmic tail and CD4 to link and increase the avidity between the APC and T cell

The number of CD4 or CD8 T cells generated is dependent on innate properties of the virus

There are more T helper cells generated than CTLs

The number of CTLs and T helper cells generated is approximately equal

There are more CTLs generated than T helper cells

Lck binds to CD3 to induce direct signalling through the TCR

Lck binds to the immunoreceptor tyrosine-based activation motifs (ITAMs) on CD4, and leads to phosphorylation

Lck, bound to CD4, leads to phosphorylation of immunoreceptor tyrosine-based activation motifs (ITAMs) on CD3

Lck binds to the TCR tail and CD4, to link and increase their avidity

CD28 is important for delivering 'signal 1' for T cell activation, and CTLA-4 is important for delivering 'signal 2'

CD28 is constitutively expressed on naïve T cells, whereas CTLA-4 is expressed on activated T cells

CD28 binds B7 (CD80 & CD86) with significantly greater affinity than CTLA-4

Only CD28 binds the B7 costimulatory ligands (CD80 & CD86) expressed on professional antigen-presenting cells

To promote cross-presentation, to activate both CD4 and CD8 T cells

To promote non-specific activation of local T cells to broaden the immune response (immune spreading)

To promote expression of the TCR on T cells

To direct T cell differentiation towards a specific cell type

Antibody can bind to C3b and cross-link bacteria and phagocyte, allowing efficient phagocytosis

The phagocyte has surface molecules that can bind to C3b and antibody

C3b and antibody can bind to surface PRRs on the phagocyte and trigger phagocytosis

C3b and antibodies can lyse the bacteria, releasing PAMPs for recognition by phagocytes (primarily macrophages)

CTLs are able to detect any cell that has been infected with any virus and kill it

CTLs are generated in the thymus

CTLs will only respond to one peptide:MHC combination

CTLs generated in response to a specific viral peptide can respond to any MHC class I molecule presenting that peptide

Migration of the infected macrophage to local draining lymph node

The down regulation of MHC expression by the infected and stressed cell

The presentation of bacterial peptide by MHC on the macrophage

The secretion of T cell proliferative cytokines from the infected macrophage