The Effect of Rh2 Phenotype on Cytotoxic T-Cell Counts.

Sub-Saharan Africa and the Caribbean countries bear a disproportionate burden of the HIV pandemic. This suggests a genetic predisposition arising from a common ancestry. A 40% HIV risk-reduction associated with Rh2 blood group was reported in a previous study by the same authors. The current study seeks to elucidate potential mechanisms for this risk reduction. Lymphocyte sub-populations and viral load measurements were achieved by routine diagnostic laboratory methods in 102 untreated HIV-1 infected patients. The results were compared across the categories of RH2 blood group. Carriage of the Rh2 antigen was associated with a higher proportion of T-cells (82±8% versus 75±10%, P=0.001), especially single-positive (CD8+) cytotoxic T-cells (64±14 versus 54±13%, P=0.004). High absolute CD8 counts were more prevalent among the Rh2-positive than the Rh2-negative subjects (90% versus 65%, p=0.023). Among the Rh2-positive subjects, the increase in CD8 count paralleled the viral load in comparison to the Rh2-negatives (r²=0.630, P<0.0001 versus r2=0.148, P<0.001, respectively). The results suggest that Rh2 enhances the CD8 counts in an HIV infection, and its cells are known to play a vital role in immunity against HIV. This probably explains the protective role observed against HIV-1 infection. [ABSTRACT FROM AUTHOR]