Nude mice lack a thymus and so don't produce:

• A. B cells
• B. T cells
• C. Plasma cells
• D. Null cells

Answer: (B)

T cells are the ones that mature in the thymus, so when a nude mouse lacks a thymus, T lymphocytes cannot develop. The thymus provides the environment for T cell maturation, selection, and education, and without it, there are effectively no mature T cells to participate in cell-mediated immunity. B cells can still be present and respond in some ways, though robust antibody responses often require help from T cells; plasma cells derive from B cells but their full activity is enhanced by T-cell signals. NK (null) cells do not depend on the thymus for development, so they are not eliminated by this thymic absence. Therefore, nude mice do not produce mature T cells.