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Scientists measured the quantity and qualities of B cells in blood samples taken from three groups of study volunteers: men who had been infected with HIV for fewer than 6 months; men who had been infected with HIV for 6 months or more; and men who were not infected with HIV.The HIV-infected men began taking ART for the first time once they entered the study. B cells make proteins called antibodies that can flag pathogens for destruction by the immune system and prevent them from infecting cells.
At the outset of the study, the number of B cells in the blood of both groups of HIV-infected men was significantly lower than the number of B cells in the blood of the uninfected men. Once the two groups of HIV-infected men began ART, however, the numbers of B cells in their blood increased significantly and to similar degrees. The scientists observed that early treatment restored resting memory B cells to the same level as that in HIV-uninfected men, but late treatment did not. Also, early ART reduced the proportion of immature B cells to the same level as that in HIV-uninfected men, but late treatment did not.Source