In patients with human immunodeficiency virus (HIV) infection, immune status can be monitored by measuring the ratio of

• A. CD3+ cells to CD8+ cells
• B. CD4+ cells to CD8+ cells
• C. Lymphocytes to monocytes
• D. T cells to B cells

Answer: (B)

Measuring the CD4+ T cell to CD8+ T cell ratio is used to monitor immune status in HIV because HIV preferentially depletes CD4+ helper T cells, causing the CD4+ count to fall and the CD4/CD8 ratio to become inverted. This ratio provides a clearer picture of immune function than looking at total lymphocytes alone, since it reflects the balance between helper and cytotoxic T cells that HIV disrupts. As the infection progresses, CD4+ cells decrease (and often CD8+ cells may increase or stay the same), driving the ratio down. Monitoring this ratio, together with absolute CD4+ counts, helps gauge immune deterioration and response to therapy. Other markers like CD3+ indicate total T cells, not the helper/cytotoxic balance, and ratios involving lymphocytes to monocytes or T cells to B cells don’t specifically reflect the HIV-driven depletion of CD4+ T cells.