T cells initiate the adaptive immune response by interacting MHC on antigen-presenting cells that have been exposed to pathogens. 

TLS Online TPP Program

#Id: 1356

#Unit 4. Cell Communication and Cell Signaling

The cytokines form a family of small, secreted signaling molecules (about 160–200 amino acids) that control growth and differentiation of cells.

TLS Online TPP Program

#Id: 1357

#Unit 4. Cell Communication and Cell Signaling

Family of Cytokines

• Interleukins

• Interferons

• Growth hormone

• Prolactin

• Granulocyte colony–stimulating factor

• Thrombopoietin

• Erythropoietin (Epo)

TLS Online TPP Program

#Id: 1358

#Unit 4. Cell Communication and Cell Signaling

GH, prolactin, G-CSF, thrombopoietin, and Epo evolved from a common ancestral protein.

TLS Online TPP Program

#Id: 1359

#Unit 4. Cell Communication and Cell Signaling

All cytokines have a similar tertiary structure consisting of four long conserved α helices folded together.

TLS Online TPP Program

#Id: 1360

#Unit 4. Cell Communication and Cell Signaling

Receptor Homodimerization GH, prolactin, G-CSF, thrombopoietin, and Epo have similar structures & they activate receptors of similar structure by forming dimers of two identical cytokine receptor proteins.

 

TLS Online TPP Program

#Id: 1361

#Unit 4. Cell Communication and Cell Signaling

Cytokine receptors activate tyrosine kinases in which receptor and kinase are separate polypeptides.