GnRH stimulates secretion of FSH and LH by gonadotropes

TLS Online TPP Program

#Id: 9920

#Unit 4. Cell Communication and Cell Signaling

Many Viruses Are Neutralized by Antibodies

Antibodies are particularly effective if they are localized at the site of viral entry into the body.

TLS Online TPP Program

#Id: 9921

#Unit 4. Cell Communication and Cell Signaling

Cell-Mediated Immunity against Virus

Both CD8+ TC cells and CD4+ TH1 cells are required components of the cell-mediated antiviral defense.

Activated TH1 cells produce IL-2, IFN-ϒ, and tumor necrosis factor-α.

TLS Online TPP Program

#Id: 9922

#Unit 4. Cell Communication and Cell Signaling

IFN-ϒ acts directly by inducing an antiviral state in nearby cells.

IL-2 acts indirectly by assisting the development of cytotoxic T lymphocyte(CTL) precursors into an effector population.

Both IL-2 and IFN-ϒ activate NK cells.

TLS Online TPP Program

#Id: 9923

#Unit 4. Cell Communication and Cell Signaling

TLS Online TPP Program

#Id: 9924

#Unit 4. Cell Communication and Cell Signaling

Viruses Employ Several Different Strategies to Evade Host Defense Mechanisms

Hepatitis C virus, inhibiting the action of PKR.

Herpes simplex virus TAP.

TLS Online TPP Program

#Id: 9925

#Unit 4. Cell Communication and Cell Signaling

Adenoviruses and cytomegalo virus use to reduce the surface expression of class I MHC molecules, 

Measles virus and HIV, reduce levels of class II MHC molecules on the surface, 

Vaccinia virus, secreting a protein that binds to the C4b complement component.