Central tolerance is established to prevent autoimmunity and occurs in primary lymphoid organs; which pair correctly identifies the organ for each cell type?

• A. Lymph nodes for both T and B cells
• B. Spleen for T cells, Lymph nodes for B cells
• C. Thymus for T cells and Bone marrow for B cells
• D. Liver for T cells, Thymus for B cells

Answer: (C)

Central tolerance eliminates self-reactive lymphocytes during development in primary lymphoid organs. T cells mature in the thymus, where strong recognition of self-antigens leads to negative selection and deletion (with some cells becoming regulatory T cells). B cells mature in the bone marrow, undergoing receptor editing, deletion, or anergy to self-antigens before entering the circulation. That pairing—T cells in the thymus and B cells in the bone marrow—reflects where central tolerance is established. The other options place T or B cells in secondary lymphoid tissues like lymph nodes or spleen, or in non-primary organs, which are involved more in peripheral tolerance and immune activation rather than central tolerance.