Stimulation and suppression of cell-mediated immunity by endosporulation antigens of Coccidioides immitis.

Theculture filtrate ofCoccidioides immitis induced toreplicate initsparasitic phase invitro, termed endosporulation antigens (EA), wasassayed forability to stimulate humanlymphocyte blastogenesis invitro. Stimulation oflymphocytes fromskin test-positive healthy subjects byEA wascomparable tostimulation by spherulin atoptimal dilutions, butEAare500times morepotent whencompared onthebasis ofweight. Bothpreparations slightly stimulated lymphocytes from skin test-negative subjects. Heating ordialysis ofEAenhanced theeffect onskin test-positive subjects, butconcentration depressed it.Concentrated EA also depressed nonspecific stimulation caused byphytohemagglutinin. Dialysis of concentrated EAreduced theability todepress responses. EAfromanavirulent strain ofC.immitis wereasstimulatory asEA froma virulent strain, but concentrating theformer didnotproduce asmuchdepression asconcentrating the latter did.A survey ofsubjects withanoptimal doseofEA inlymphocyte transformation showed that EAcould separate skintest-positive from-negative subjects aswellasspherulin could. Thesurvey also showedthat aAcpm(the difference ofincorporated counts oftritiated thymidine perminute inthepresence orabsence ofthereagent) of10,000 isuseful forthis separation. These results also indicate thepresence ofsuppressive substances inEA whichareonlypartially dialyzable andwhich weresignificantly moreprominent inapreparation fromthe virulent strain. Coccidioidin, aculture filtrate ofCoccidioides immitis initssaprophytic mycelial phase, and spherulin, alysate ofspherules (parasitic phase,