Human B-lymphoid differentiation: normal versus malignant.

In this review the features of B-cell development and differentiation are described for the bone marrow and peripheral B-cell system, in particular that in lymph nodes follicles. These features show many similarities to those of malignant B-cell populations. Frequently the "normal counterparts" of malignant B lineage cells are seen in particularly high frequency in the foetal lymphoid tissues. For example, foetal bone marrow shows abundant CD10+ precursors and foetal lymph nodes contain many CD5+ B cells. These similarities contribute to a better understanding of B-cell malignancy. On the other hand they provide observations also useful in interpretation of immunodeficiency such as X-linked agammaglobulinaemia and lymph nodes after HIV-1 infection. The identification of target cells in lymphoid malignancies will be important for understanding the mechanism of tumour development because the gene alterations also show target cell specificity.