Studies on the quantitative relationship between specific antigen recognition and manifestation in delayed hypersensitivity.

Delayed skin reactions or peritoneal cell migration inhibition were elicited in guinea-pigs or rats with egg albumin, diphtheria toxoid, or tuberculin-purified protein derivative either separately or with various combinations of two antigens. When the skin reactions or migration inhibition with the component antigens alone were relatively strong, the corresponding combination elicited weaker reactions than calculated assuming that the antigens would add upon each other independently, i.e. the non-specific phase was limiting the manifestation. When the reactivity to both components was undetectable or very weak, the combination elicited stronger reactions than calculated, implying synergism of antigen recognition. The combinations of two weakly positive or intermediate reactivities were close to the calculated values in both the diameter of erythema, skin thickness and migration percentage. These results may help in assessing the biological significance of findings in delayed hypersensitivity: even minor differences in strong manifestations may mean great differences in terms of specific lymphocytes, while marginal changes of antigen recognition may lead to apparently great changes of manifestation, when very weak reactivities are measured.