Helper function of rat spleen cells reactive with guinea pig serum

Treatment of rat spleen cells with normal guinea pig serum (GPS) has been shown to produce a significant loss of responsiveness to stimulation with either Con A or PHA. This phenomenon was seen even when the spleen cells were triggered with mitogens up to 96 hr after treatment with GPS, suggesting that GPS had produced a long-lasting alteration in some cells or removed a cell subpopulation. Glass-wool non-adherent spleen cells, known to produce greater responses that unfractionated spleen cells, also had their responses to Con A and PHA reduced by GPS treatment though the response was still greater than that of untreated, unfractionated cells, suggesting that the actual responder cells had been spared by GPS. Suppressor cells did not appear to be the target of GPS because such an effect would have resulted in increased responsiveness and the opposite result was obtained. That a helper cell was affected by GPS was suggested by the following observations: a) the virtually unresponsive GPS-treated spleen cells produced greater than normal responses after removal of glass-wool-adherent suppressor cells; b) the response of glass-wool-nonadherent spleen cells was significantly decreased after GPS treatment; and c) mixtures containing equal numbers of glass-wool-nonadherent and GPS-treated spleen cells also showed reduced responsiveness after GPS treatment.