ULTRAVIOLET-B IRRADIATION OF LEUKAPHERESIS PRODUCTS - DOSE-RESPONSE RELATIONSHIP WITH THE MIXED LYMPHOCYTE-REACTION

Ultraviolet-B (UVB) irradiation of blood constituents intensifies thei r anti-rejection effect in pretransplant donor-specific transfusions. UVB-induced inhibition of the mixed lymphocyte reaction (MLR) between WE-irradiated donor cells and prospective recipient cells is a predica tor of this anti-rejection effect. In order to define the dose-respons e relationship between the incident UVB irradiation on leukocyte conce ntrates and subsequent inhibition of their MLR responses, we collected 4 +/- 2 x 10(9) leukocytes (93 +/- 7% lymphocytes) in 200 ml plasma f rom each of three volunteers by leukapheresis and exposed them to rapi d, serial doses of UVB irradiation which was delivered by a blood prod uct irradiator (4R4440 UVB Irradiator, Baxter, Inc) with aliquots remo ved between doses. Lymphocytes from each aliquot were placed in MLR wi th panel donors and studied in three groups: 1) the panel donor cells were gamma-irradiated (1,500 rads) (i.e., only the UVB-irradiated cell s could proliferate), 2) the UVB-irradiated cells were gamma-irradiate d (i.e., only the panel lymphocytes could proliferate), and 3) no gamm a-irradiation (i.e., both cell populations could proliferate). Each gr oup had a similar UVB dose-related diminution in the MLR (p = .79, ANO VA). A single dose of 6 J/cm(2) extinguished the MLR to baseline in al l groups. This dose should theoretically prevent transfused cells from producing either graft-versus-host disease or allosensitization, and might heighten their tolerogenic effect. This dose will be employed in our study of donor-specific leukocyte transfusion in clinical renal t ransplantation. (C) 1996 Wiley-Liss, Inc.