A B S T R A C19S serum fractions with anti-YE antibody activity did not release histamine from normal human peripheral blood leukocytes, whereas specific rabbit anti-yE antisera consistently induced leukocytic histamine release. Moreover, macroglobulin fractions with anti-yE activity did not block allergen-specific leukocyte histamine release induced by in vitro leukocyte challenge with allergens such as Bermuda grass and leukocytes from allergic donors. In some instances 19S human serum

A B S T R A C T 42 human sera showing in vitro cytotoxic activity of restricted or broad HL-A specificities with test human lymphocytes were studied for the molecular and immunoglobulin class of cytotoxic antibody using sucrose gradient separations, DEAE-cellulose chromatography, and Sephadex G-200 gel filtration. Sera originated from patients with previous multiple pregnancies (19), multiply transfused patients (8), subacute bacterial endocarditis (4), systemic lupus (2), and human umbilical cord sera (9). In 32 of 42 instances, predominant cytotoxic activity was found in high molecular weight gradient fractions; however, DEAE chromatographic separations revealed cytotoxic activity in initial buffer fractions containing primarily -vG globulin. Gradient separations of cytotoxic activity within initial 'vG DEAE fractions showed localization of cytotoxicity only in high molecular weight materials.Confirmation of high molecular weight YG cytotoxic activity was obtained by resistance to mercaptoethanol treatment, abolition of activity after absorption only with specific anti-yG antisera, and by the finding that high molecular weight cytotoxic activity in gradients or gel filtration run at neutral pH 7.4 became 7S when separations were rerun at an acidic pH of 4.0. Such 7S activity again became rapidly sedimenting when the same fractions were again rerun in gradients at neutral pH.19S iM cytotoxic activity was documented in a panel of 15 human sera containing anti-"I" cold agglutinins. In this instance the cytotoxic activity appeared to be related to the cold agglutinin antibody since it was mercaptoethanol sensitive and could be demonstrated in monoclonal antibody eluates containing primarily -yM.

Rabbit antisera were made against pooled normal human lymphocytes and against those from patients with active rheumatoid arthritis. Sera were subsequently absorbed to remove antibody to human erythrocytes and plasma proteins. Most antilymphocyte antisera showed considerable cytotoxic or complement fixing antibody after immunization, however a striking deficit (6 of 12 animals) in the activity of the antisera against RA lymphocytes was noted when blast transformation of lymphocytes was used as a test of antilymphocyte serum (ALS) antibody.