Antigen-induced suppression of the in vitro lymphocyte response to different antigens and mitogens

Certain concentrations of antigen stimulated DNA synthesis in sensitized human lymphocytes cultivated in vitro, higher and lower concentrations being less stimulatory. The simultaneous addition of two antigens in low concentrations to the same cells caused an additive response. The decreased response to a high antigen dose did not affect the capacity of the cells to respond to the simultaneous addition of another antigen, as determined at the population level as well as at the cellular level by autoradiography. Presumably specific immunological paralysis was induced by high antigen doses.

Addition of low antigen doses for 1–3 days to human sensitized lymphocytes cultivated in vitro resulted in decreased DNA synthesis as a response to the same antigen added in an optimal dose. Suppression of DNA synthesis was not caused by induction of tolerance or antibody suppression, because the cells also failed to respond to an unrelated antigen and to non-specific mitogens, such as PHA and ALS. Most likely the suppressed response after antigen pretreatment represents a phenomenon analogous to antigenic competition, although this term is not appropriate, since there need not be competition between antigens for a detectable effect. No soluble mediators of suppression could be demonstrated in the supernatant of suppressed cultures.

Cross-reactivity studies of horse, goat and rabbit anti-lymphocyte globulin

In the sera of ten normal humans and twenty-eight candidates for organ transplantation, the passive haemagglutination test detected a 50% incidence of preformed antibodies of low titre directed against horse serum. Such antibodies were also found to cross react with goat or rabbit sera in most instances. Seventeen of the organ recipients were later studied after the institution of treatment with horse antihuman-lymphocyte globulin (ALG). The incidence of anti-horse-serum antibodies rose to 100%. At the same time, an increased activity against goat serum developed; cross-reactions against rabbit serum were also demonstrated but to a less pronounced degree. With immunoelectrophoresis and Ouchterlony diffusion tests, it was shown that the cross-reactivity was to similar although not necessarily identical protein components of the different heterologous sera.

These data suggest that there is an inherent risk in switching from one ALG to another, particularly if horse and goat derivatives are used sequentially. Since rabbit ALG does not cross react so extensively with horse or goat serum it would be predicted to be a relatively safer second-line agent.

These expectations seemed to have been realized in six patients who were given more than one kind of ALG, always beginning with horse globulin. When goat ALG was administered second, anaphylactic reactions tended to appear early, but when the rabbit product was given second or third, it was relatively well tolerated.

Clinical reactions and serologic changes after the administration of heterologous antilymphocyte globulin to human recipients of renal homografts

Clinical reactions and serologic changes after intramuscular administration of horse anti-human lymphocyte globulin (ALG) were studied in 53 human recipients of renal homografts. The ALG was used as an adjuvant immunosuppressive drug. In the usual case 47 injections were given over a 4-month period. All patients had pain, tenderness, erythema, and swelling at the injection sites. Benign systemic side effects included fever in all cases, hives in eight cases, rash in five, pruritus in five, arthralgia in three, and periorbital edema in one. Anaphylactic reactions occurred in 11 cases. These were easily treated, and there was complete recovery in every instance within 90 min. In eight of these cases the ALG administration was discontinued. Subsequent injections were given in the other three. Four of 11 patients tested had positive skin tests to ALG before therapy. Antibodies against sheep red blood cells developed during therapy in 39 of 40 patients; 10 reached titers as high as 1:128 to 1:512. Precipitin antibodies as measured with an electroimmunodiffusion technique developed in 36 of 40 patients. All three immunologic tests were of value in predicting the probability of an anaphylactic reaction, but the discrimination was imperfect Immunoelectrophoretic studies of sera from 13 patients showed antibodies to horse beta globulins in all cases, to alpha globulins in 9 cases, and to gamma globulins in only 1. This finding indicates that a safer ALG could be made by removing the trace quantities of alpha and beta globulins from the immunologically more active gamma globulins.