Effect of encephlitogenic protein. PPD and tetanus toxoid on leukocyte migration in agarose. A study of "cross-reactivity".

The reactivity to three antigens: bovine encephalitogenic protein (EP), PPD, and tetanus toxoid, was studied with blood leukocytes from healthy humans using Clausen's (5) leukocyte migration in agarose technique. There is an obvious correlation between the reaction of EP (all concentrations studied) and to low concentrations of PPD; and between the reactivity to low concentrations of EP and low concentrations of tetanus toxoid. After vaccination with tetanus vaccine, a marked increase in reactivity to the toxoid sometimes occurred; at the same time, a marked reactivity to EP appeared. Various explanations are discussed: a true immunological cross-reactivity, that the correlations are due to a variability in individual response with respect to lymphokine production, and that BCG and tetanus vaccinations produce an adjuvant effect increasing a pre-existing low reactivity to EP.