Discrepancy between skin reactivity and blastogenic activity of fractionated PHA-P

Firstly, it was reported that phytohemagglutinin P (PHA-P) can induce the immediate skin reaction besides the delayed one. 70 out of 80 cases (87.5%) gave positive immediate reactions with 1 mug of PHA-P. There was a close correlation between the radioallergosorbent test (RAST) counts against PHA-P and the total IgE value or erythematous diameter of the immediate skin reactions. Absorption with anti-IgE or PHA-P reduced the RAST counts against PHA-P to 79 and 56% of their initial values, respectively, but did not effect the RAST counts against steptokinase-streptodornase (SK-SD). These results suggest that the immediate skin reaction might be induced by specific IgE antibody against PHA-P. Secondly, using three fractions of PHA-P obtained by Sephadex G-200 gel filtration, skin test and RAST in humans, ACA in rats, and 3H-thymidine incorporation into human leukocytes, were carried out and data obtained that showed some discrepancy between them. That is, on skin testing, it was shown that all of the three fractions (fr.) had the ability to elicit the immediate and delayed skin reaction in humans and rats with the order of fr. 1, 2 and 3, and it was confirmed by RAST. On the other hand, the leukocyte-stimulating activity resided in fr. 1 and 2, while fr. 3, which seemed to be a group of subunits with a molecular weight of around 35,000, had almost no activity. These findings have been discussed in view of the earlier studies on the structure of PHA-P