OVA-Tg CD4⁺ cells show hyporesponsiveness following primary antigen stimulation in the presence of spleen from TLI-preconditioned mice.

(A) Purified naive OVA-Tg CD4⁺ were cultured with increasing concentrations of OVA peptide and APCs from either untreated BALB/c (BALB/c, ●) or TLI-preconditioned BALB/c mice (TLI, ○). After 48 hours, proliferation was measured by ³H-thymidine incorporation. (B) OVA-Tg cells were cultured as in (A) with OVA peptide and APCs from either untreated (BALB/c, solid symbols) or TLI-preconditioned (TLI, open symbols) BALB/c mouse spleen without (circles) or with (squares) anti-CD28. Proliferation was measured by³H-thymidine incorporation. Symbols represent the mean ± SD of triplicate wells for one representative experiment from 3 separate experiments. APCs alone did not proliferate in response to increasing OVA peptide (not shown).