Differences in cellular immunity between humans and chimpanzees in relation to their relative resistance to aids

Abstract

Chimpanzees are the only animal species that can be infected with HIV-1. Infection kinetics in both humans and chimpanzees are similar, in contrast to humans, chimpanzees do not show any signs of immunodeficiency for many years. In this thesis specific aspects of the human and chimpanzee immune system are compared to unravel the differences in cellular immune responses in relation to HIV-1 infection. Human CD4 T-cells have less CD40L expression once the viral envelope is bound to the CD4 receptor. This is also seen in chimpanzees, but this occurs at a 5 fold higher antigen level, leading to the conclusion that chimpanzees are less sensitive for immunodeficiency. Little information is known about chimpanzee NK cells. The majority of this thesis describes the differences and overlaps between human and chimpanzee NK cells, with a focus on activatory receptors. Chimpanzee NK cells show small differences in the expression of these receptors, leading to the conclusion that these cells need more triggers than ligand binding, resulting in the hypothesis that chimpanzee NK cells are in less risk of over activation, which is seen in human lymphocytes. This overactivation leads to an exhausted immune system, which is thought to be the basis for immunodeficiency.