Preliminary identification of a low molecular weight serological mediator in XXXX .

@entity1 @entity14687 @entity2631
Sixteen @entity1 with @entity14687 were skin tested with their own serum, IO with autologous plasma and five with serum that had been heated to 56 degrees C to inactivate complement. Eight showed a weal and flare response to whole serum, four to plasma and five to heat-treated serum. All serum-positive @entity1 showed the same response to their own plasma and to heated serum, indicating that the mediator concerned is not generated by clotting and is not dependent on a functioning complement pathway. Three control subjects were negative to autologous serum, plasma and heated serum. @entity2631 was demonstrated in five serum-positive @entity1 on reinjection of the same site with autologous serum on 3 consecutive days. This raises the possibility that the serological mediator may be acting by mast cell degranulation or directly on receptors in blood vessels and that repeated injections could induce a change in the number of receptors. Passage of whole autologous serum from four serum-positive @entity1 through ultrafiltration membranes showed that fractions with a molecular weight of less than 30,000 daltons were still able to produce a positive skin test response, but those less than 1000 daltons were not. All serum fractions from two serum-negative @entity1 and three normal controls were negative. Whole autologous serum from five serum-positive @entity1 and two control subjects were separated by column chromatography. On skin testing with pooled fractions, the greatest response was produced by fractions of 10,000-15,000 daltons in the serum-positive @entity1 , but there was no response in the controls.
