1. By: Chris Baumgartner Christine Keogh Ali Lauer Carolyn McGrath Introduction of CD4

2. Helper T-Cells  Helps to determine immune response by secreting cytokines.  Made aware of foreign antigens by MHC II.  Essential for activating B-cells and other T- Cells.  Must have CD4 protein which recognizes MHC II.

3. CD4  Two teams of HHMI researchers determined the structure of gp41, a protein fragment from the surface of HIV that penetrates a cell's membrane like a sewing- machine needle. This allows the virus to "fuse" with the membrane of the cell and gain access to the cell's reproductive machinery  http://www.hhmi.org/news/keyhiv.html

4. Function of CD4  Allows scientists to identify and separate helper T- cells  Essential to assist helper T cells to stimulate immune responsiveness of other lymphocytes.  CD4’s ability to recognize foreign invaders is due to its ability to strengthen the union between helper T cells and antigen presenting partners  www.ams-assn.org/special/hib/neytine/briefing/ed4.htm

5. Function of CD4 www.crixivan2.com

6. CD4  Three main stages of disease development described by variations in the levels of CD4 cells.  Shortly after HIV infection, high levels of HIV in the blood cause a sharp decline in CD4 cell levels that may decrease to half their original quantity before they start to rise again.  During the chronic stage, which may last from months to years, the CD4 cell count stabilizes, and the HIV-infected individual may not experience symptoms.  In the advanced stage, the rate at which the virus reproduces or "replicates" surpasses the rate of CD4 cell turnover, making the body more susceptible to a variety of AIDS-defining illnesses, such as Pneumocystis carinii pneumonia (PCP).Pneumocystis carinii pneumonia  As the viral load rapidly increases unchecked and the CD4 cell counts decline, these illnesses that signal late-stage infection, eventually lead to death