The Effect of Low-dose Irradiation on Unstimulated and PHA-stimulated Human Lymphocyte Subsets

Abstract

A culture system was used to evaluate the radiosensitivity of CD 4⁺ and CD 8⁺ T cells, Leu 19⁺ cells, and B cells obtained from normal adult males. Unstimulated CD 8⁺ lymphocytes (D₀ = 55 cGy) were twice as radiosensitive as CD 4⁺ cells (D₀ = 115 cGy). B cells had an intermediate radiosensitivity (D₀ = 100 cGy). Leu 19⁺ cells were much more radioresistant and expressed a D₀ of 550 cGy. When lymphoid cells were irradiated 1 or 4 days before phytohemagglutinin (PHA) stimulation, they were more radiosensitive than if they were first stimulated with PHA and then irradiated. When lymphoid cells were irradiated 1 h after PHA stimulation each lymphocyte subset was characterized by an increase in the D₀ to 150 cGy for B cells to 290 cGy for CD4⁺ cells, and to 240 cGy for CD8⁺ cells. In contrast, Leu 19⁺ cells exhibited a decrease in their D₀ to 290 cGy after they were stimulated by PHA.