TCR + MHC + antigen

TCR and MHC StructureClass I

•expressed by nearly all cells •present antigens to TC cells•cytosolic pathway (endogenous antigen presentation)

Class II •expressed only by APCs•present antigens to TH cells•endocytic pathway (exogenous antigen presentation)

Antigen Processing Comparison

Antigen Presentation/Signaling

Antigen Presentation/Signaling

Antigen Presentation/Signaling

Antigen Presentation/Signaling

Antigen Presentation/Signaling

Cytotoxic Action

Cytotoxic Action

Cytokines (Chapter 12)Cytokines•Secreted protein

• Low molecular-weight

• Regulate intensity/duration of immune response

• Variety of effects on: -lymphocytes-other immune cells

•See Appendix II

Cytokines: Types of ActionAutocrine – A condition in which the cell acted on by a cytokine is the source of the cytokine.

Paracrine – Regulatory secretions that arrive by diffusion from a nearby cellular source.

Endocrine – Regulatory secretions that pass from the producer cell to target cell by via the bloodstream.

Cytokine AttributesPleiotropy – a given cytokine has different biological effects on different target cells.

Cytokine AttributesRedundancy – When two or more cytokines the mediate similar functions.

Synergy - When the combined effect of two cytokines on cellular activity is greater than the effects of the individual cytokine.

Cytokine AttributesAntagonism – the effects of one cytokine inhibit or offset the effects of another cytokine.

Target Cell Effect____________

Cytokine AttributesCascade Induction – when the action of one cytokine on a target cell induces that cell to produce one or more other cytokines, which in turn may induce other target cells to produce other cytokines.

Biological Functions of Cytokines

Classification of Cytokines Cytokine classification based their receptors:

•Immunoglobulin superfamily•Class I cytokine (Hematopoietin)•Class II cytokine (Interferon)•TNF family•Chemokine family

Classification of Cytokines