Benzo(a)pyrene

(found in cigarette smoke & coal tar) undergoes metabolic activation by cytochrome P-450 in the lungs to form a potent mutagen

TLS Online TPP Program

#Id: 1766

#Unit 4. Cell Communication and Cell Signaling

Activated T cells express increased levels of Fas and FasL. In both B and T cells, engagement of Fas by FasL induces a rapid apoptotic death known as activation-induced cell death (AICD).

TLS Online TPP Program

#Id: 1767

#Unit 4. Cell Communication and Cell Signaling

Tolerogens- Antigens that induce tolerance

TLS Online TPP Program

#Id: 1768

#Unit 4. Cell Communication and Cell Signaling

Factors that promote tolerance rather than stimulation

a. High doses of antigen

b. Long-term persistence of antigen in the host

c. Intravenous or oral introduction

TLS Online TPP Program

#Id: 1769

#Unit 4. Cell Communication and Cell Signaling

Absence of adjuvants

a. Low levels of costimulation

b. Presentation of antigen by immature

TLS Online TPP Program

#Id: 1770

#Unit 4. Cell Communication and Cell Signaling

CD28 on the T cell and CD80/86 (B7) on the APC provided the costimulatory signal required for T-cell activation.

TLS Online TPP Program

#Id: 1771

#Unit 4. Cell Communication and Cell Signaling

An antigen presented to T cells without appropriate costimulation results in a form of tolerance known as anergy.