Frequency of infected cells in PBMC of LTS and individuals who progressed to AIDS (Progressors). PBMC from LTS and Progressors were serially diluted 10-fold and cultured with PHA-stimulated PBMC from HIV seronegative donors. The cocultures were evaluated for the lowest dilution of cells which produced positive particle-associated reverse transcriptase activity20(≥10⁴ cpm/mL) in the culture fluids over a 30-day culture period. Each point represents the result from a different individual. Bars represent the mean value for the data obtained from the two groups of individuals tested. The number of infected cells in the peripheral blood of LTS and Progressors was statistically different (P = .01) using the Mann-Whitney U test.