Chemistry of a low molecular weight ragweed pollen allergen RA5, and association of human responsiveness to RA5 with HL-A7 cross-reacting group.

A protein allergen, Ra5, was isolated by column chromatographic procedures from the aqueous extract of short ragweed pollen by Lapkoff and Goodfriend. The allergen was obtained in a highly homogenous form, was devoid of carbohydrate and had the low molecular weight of 5100 daltons. A report will be given of studies by Marsh, Bias, Hsu and Goodfriend on the cutaneous activity of Ra5 in 105 antigen E-sensitive patients along with HL-A typing of these patients. The results have demonstrated a highly significant association between sensitivity to Ra5 and possession of a histocompatibility antigen of the HL-A7 cross-reacting group (creg). By analogy with studies in inbred strains of mice, this finding suggests control of human sensitivity to allergens by immune response genes. A brief account will also be given of studies on the primary structure of allergen Ra5 by Mole, Goodfriend, Lapkoff, Kehoe and Capra which have to date yielded the complete amino acid sequence of this protein.