Those without a history of injection drug use had statistically (p < 0.01) higher nadir CD4+ lymphocyte count, and were significantly less likely to be Black, non-Hispanic (and more likely to be White or Hispanic), had higher education and income, were more likely to be employed, were less likely to be current smokers or drinkers, less likely to have ever been diagnosed with AIDS, and initiated HAART earlier (pre-1998) than those with a history of injection drug use. This evidence concerns the gene CD4 and AIDS.