Question

1. Which defect would have a more crippling effect on the immune system, a complete loss of calnexin function or a complete loss of CD4 function. Justify your answer and include the normal function of each molecule?

Answer 1

Part I	Calnexin	CD4
It is a chaperone and helps in protein folding and its control of quality. It ensures about the proper folding and assembly of protein. It acts to retain the unfolded structure of protein. It plays an essential role in regulation of calcium in endoplasmic reticulum. It sequesters free calcium and works like buffer. It is a signaling complex and is associated with thymocyte maturation. It has a leading role in receptor mediated endocytosis at synapse.	CD4 represents cluster of differentiation 4. It is an essential glycoprotein located over the surface of dendritic cells, helper T cells, monocytes and macrophages. CD4+ T helper cells are white blood cells that are integral part of human immune system. They have modulatory role I n sending the signals to other immune cells, that is why, they are termed as helper CD4 cells.
Part II	One of the important characteristic features of HIV is steady loss of CD4-T cells. An imbalance in CD4-T is associated with decline of immunity which could be lethal for an organism. If HIV infection is left untreated, the HIV virus enters the cells and propagatescausing the death of CD4 cells. The remaining cells infect the healthy cells and progress the disease. Thus, loss of CD4-Tlymphocyte will produce an adverse effect over proper immune response.