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CYTOKINES. Cytokines are a diverse group of non-antibody proteins released by cells that act as intercellular mediators, especially in immune processes. Definition. - PowerPoint PPT Presentation
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CYTOKINESCytokines are a diverse group of non-antibody proteins released by cells that act as intercellular mediators, especially in immune processes
Definition
Cytokines are a diverse group of non-antibody proteins released by cells that act as intercellular mediators, especially in immune processes
Cytokines…..
Low molecular weight soluble proteins (polypeptides) produced in response to microbes and other antigens
They act via cell surface receptors to mediate and regulate the amplitude and duration of the immune-inflammatory responses, through activation of macrophages, controlling growth and differentiation of T and B cells
General Properties
1.Produced by cells involved in both natural and specific immunity
2. Mediate and regulate immune and inflammatory responses
3. Secretion is brief and limited not stored as pre-formed molecules
4. Synthesis is initiated by new short-lived gene transcription
mRNA is short-lived 5. Pleiotropic -different cell types to
secrete the same cytokine or for a single cytokine to act on several different cell types
•6. Redundancy -similar functions can be stimulated by different cytokines. Receptors for cytokines that can be grouped into families in which one subunit is common to all members.
7. Often influence the synthesis of other cytokines
They can produce cascades, or enhance or suppress production of other cytokines
They exert positive or negative regulatory mechanisms for immune inflammatory responses
8. Often influence the action of other cytokines. antagonistic -cytokines causing opposing activities
additive - two or more cytokines acting together synergistic -two or more cytokines acting
together (greater than additive)
8. Bind to specific receptors on target cells with high affinity..
9. Cellular responses to cytokines are generally slow (hours), require new mRNA and protein synthesis
Major Histocompatibility Complex
MHC
The Cellular mediated immune system relies on many regulatory mechanisms and it main controller is Major Histocompatibility Complex (Mhc).
MHC
MHC molecules are cell surface receptors that bind antigen fragments and display them to various cells of the immune system, most importantly T-cells.
Major Histocompatibility Complex
The binding of peptides by an MHC-I or MHC-II molecule is the selective event
Permits the cell expressing the MHC molecule (APC) to sample
1. its own proteins (in the case of MHC-I)
2. the antigen proteins ingested (in the case of MHC-II).
MHC I vs MHC IIFeature MHC Class I MHC class II
Polypeptide Chain
α (44-47 kD)2 (12 kD)
α (32-34 kD) (29-32 kD)
Location of antigen peptide bind
α1 and α2 domains α1 and 1 domains
Size of antigen peptide
8-11 residue 10-30 residue
Nomenclature HLA-A, HLA-B, HLA-C
HLA-DP, HLA-DQ HLA-DR