Aberrant immunoregulation of transferred T cells in SCID mice reconstituted with BALB/c lymphocytes and challenged with SEB.

(A) Deletion: BALB/c (left panel) or sublethally irradiated SCID mice reconstituted with 2 × 10⁷ BALB/c spleen cells and PLNCs (right panel) were injected with SEB. The percentage CD4⁺Vβ8⁺ and CD4⁺Vβ6⁺ cells in pooled axillary, mesenteric, and inguinal lymph node preparations were then determined at various times. Whereas SEB-reactive cells increase rapidly in both BALB/c and SCID recipients, they are deleted much more rapidly in the former. In contrast, CD4⁺Vβ6⁺ T cells, which are not SAg responsive, do not respond to SAg injection. The mean ± SE from n separate animals are shown (CD4⁺Vβ8⁺ T cells in SCID mice, n = 2, 6, 18, 2, and 5 for days 3, 4, 11, 15, and 20, respectively; CD4⁺Vβ6⁺ T cells in SCID mice, n = 3 for each time point; CD4⁺Vβ8⁺ T cells in BALB/c mice, n = 10 for each time point). B: The percentage of CD4⁺Vβ8⁺ T cells in SCID mice that were reconstituted with BALB/c spleen cells but were not injected with SEB, n = 16. (B) Anergy: CD4⁺V,8⁺ PLNC T-cell percentages in BALB/c and BALB/c reconstituted SCID mice (both naive and challenged with SEB 10 days earlier), were quantified flow cytometrically and were adjusted to 2 × 10⁵ cells/mL in complete medium. Irradiated (2000 cGy) BALB/c spleen filler cells and CD4⁺Vβ8⁺ T cells (2 × 10⁶cells/mL each), were cultured together in the presence of 1 μg/mL SEB. Proliferation of SEB-challenged cultures (filled bars) was measured 72 hours later and compared to control cultures without added SEB (open bars). Decreased SEB responses were observed in vitro using cells from BALB/c mice previously challenged with SEB, but not if such BALB/c cells were first transferred into SCID hosts. The means ± SE of a representative experiment (n = 4 for each bar) are shown. The experiment was repeated 3 times with similar results. (C) Mortality: BALB/c mice (n = 6) and reconstituted SCID mice (n = 9; 2 × 10⁷ BALB/c spleen cells and PLNCs transferred) were injected with SEB immediately following transfer and again 48 hours later. Mortality was scored 2 days after the second injection.