Induction of impaired activation of lymphocytes by suppressive factor in Crohn's disease patients

Lymphocyte proliferative response to phytohemagglutinin (PHA) and relevance of serum factors to the response were studied in 12 patients with Crohn's disease (CD). The lymphocyte proliferative response was markedly reduced in patients with Crohn's disease (S.I. = 38.8 ± 36.8) (mean ± SD), as compared with normal controls (S.I. = 100.6 ± 28.6) (p < 0.01). In addition, the effect of sera from patients with CD or 10 patients with ulcerative colitis (UC) who had extremely impaired lymphocyte responsiveness to PHA on the proliferative response to normal lymphocytes to PHA was also measured. Sera from CD patients had a marked suppressive effect on the blastogenesis of normal lymphocytes (S.I. = 46.4 ± 28.5), as compared with normal sera (S.I. = 126.2 ± 14.7) (p < 0.001). On the other hand, UC sera did not suppress the blastogenesis of normal lymphocytes (S.I. = 114.9 ± 27.7). Moreover, serum immunosuppressive acidic protein (IAP) levels in patients' sera were measured by single radial immunodiffusion assay. A marked increase in serum IAP levels was revealed both in CD patients (780 ± 270 μg/ml) and in UC patients (601 ± 278 μg/ml), as compared with normal controls (376 ± 92 μg/ml) (p < 0.001). But there was no precise correlation between the suppressive effect of sera and serum IAP levels in patients with CD. Thus, we demonstrated an impairment of the lymphocyte responsiveness to PHA in CD patients and the possible existence of immunosuppressive factors which is not identical with IAP in the sera from patients with CD.