VARIANCE IN THE RESISTANCE OF MURINE EARLY BONE-MARROW B-CELLS TO A DEFICIENCY IN ZINC

Little is known of the effects of nutritional deficiencies on lymphopo ietic processes. Nevertheless, deficiencies in zinc adversely affect i mmune function causing thymic atrophy and lymphopenia in both humans a nd animals. Previous studies of the effects of zinc deficiency (ZD) on lymphopoiesis in adult mice indicated that a suboptimal intake of zin c caused a 50% or more depletion of the marrow of developing B cells. Thus, interference in the production of lymphocytes by ZD appeared to be a significant factor in the loss of host defence capacity. In the c urrent study three-colour immunofluorescence phenotyping of early bone marrow B lymphocytes (B220(+) immunoglobulin(-)) using flow cytometry demonstrated that a 27-day period of ZD caused a 50-70% decline in pr e-B cells (B220(+) CD43(-) immunoglobulin M (IgM)(-)) for moderate and severely zinc-deficient mice, respectively. Conversely, early pro-B c ells (B220(+) CD43(+) 6C3(-)) and late pro-B cells (B220(+) CD43(+) 6C 3(+)) exhibited little or no change in their distribution within the m arrow. Indeed, the greater resistance of pro-B cells resulted in a 50% increase in the proportion of this subset within the B-cell compartme nt of the marrow as the deficiency in zinc advanced. Collectively, the data indicate that the B-cell compartment of the marrow is substantia lly altered by ZD and the stage specific sensitivity noted among early B cells may be related to chronically elevated levels of glucocortico ids present during ZD or other parameters that affect their survival a nd resistance to apoptosis.