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Phenotypic aberrations of CD3+ and CD4+ cells and functional impairments of lymphocytes at low-level occupational exposure to lead.

To study the immunological effects of low-level occupational exposure to lead, we have examined the phenotypic parameters and functional integrity of peripheral blood lymphocytes in a group of firearms instructors and compared the data to those obtained from healthy unexposed controls. Our results indicate that, among individuals with mildly elevated blood lead levels (> 25 micrograms/dl), detrimental effects on the host's immune functions occur. Such dysfunctions are multicellular as to mechanism and dose dependent in nature. The absolute percentage and number of CD3+ and CD4+ cells were significantly reduced, while the values for CD8+ cells were unchanged. Functional integrity of T cells as determined by responses to mitogens was impaired while that of T-cell-dependent B-lymphocyte function appeared to be within normal range at all stages of maturation. These data suggest the presence of a defective feedback loop which regulates T-cell-dependent functions and cell-to-cell cooperation. Furthermore, the marked deficiency in MLC responses that was also observed suggests that the adverse effect of lead may be due to its high affinity for the TCR and HLA-DR surface receptors thereby interfering with antigen processing from monocytes to T lymphocytes.