Contribution of cell-to-cell contact to HLIL-mediated suppression of PBMC responses. The effects of incubating HLILs adjacent to paired PBMCs but separated from direct contact by transwell tissue-culture inserts. Cultures were stimulated with mitogen (ConA), recall antigen (PPD), or primary antigen (KLH). The vertical axis indicates IFN-γ secretion and proliferative responses expressed as a percentage of responses obtained from PBMCs cultured alone (up to 100% maximum). The results for samples from individual patients are linked by solid lines. Each patient (n = 10) is identified by a symbol as in Figure 2.