A 40-year-old man has been infected with HIV for the past 10 years. During this time, he has had several bouts of oral candidiasis, but no major illnesses. He is now diagnosed with Kaposi sarcoma involving the skin. He has had a 7-kg weight loss in the past 6 months. Laboratory studies show the HIV-1 RNA viral load is currently 60,000 copies/mL. Which of the following types of cells is most depleted in his lymph nodes?

As HIV infection progresses, there is continuing, gradual loss of CD4+ cells. In the clinically latent phase of the infection, CD4+ cells continue to be replaced, but there is ongoing loss, and the stage of clinical AIDS is reached when the peripheral CD4+ count decreases to less than 200/mL, which usually occurs over 8 to 10 years. At this point, the risk of development of opportunistic infections and neoplasms typical of AIDS increases greatly. The extent of viremia also is an indication of the progression of HIV infection; an increase in HIV-1 RNA levels is seen as immunologic containment of HIV fails. In HIV infection, the numbers of CD8+ lymphocytes tend to be maintained. Cells of the granulocytic series are relatively unaffected, although patients with AIDS may have cytopenias. Follicular dendritic cells can be infected by HIV and pass the virions to CD4+ cells and macrophages, but the follicular dendritic cells and the macrophages are not destroyed in large numbers by the virus and can become a reservoir for infection. Natural killer cells, CD19+ B cells, and plasma cells are not directly affected by HIV.