IGE SPECIFIC IMMUNE-RESPONSES TO AN AFRICAN GRASS (KIKUYU, PENNISETUM-CLANDESTINUM)

Kikuyu grass (Pennisetum clandestinum) is widely used as a grazing pas ture in Africa and, although it is extensively cultivated as a lawn fo r sports fields and domestic gardens, its allergenicity has never been studied in vitro. Using an extract of Kikuyu grass pollen, polyacryla mide gel electrophoresis, Western blotting and a monoclonal anti-human IgE antibody, the specific IgE binding, in the serum of 160 allergic and non-allergic patients in the Cape Town area, to a Kikuyu grass ext ract was studied. IgE in the sera of 43/104 known grass-allergic indiv iduals bound to Kikuyu grass on the Western blots. In addition, 4/28 ' non-allergic' control subjects were found to have Kikuyu grass-specifi c IgE. Five different profiles of specific IgE reactivity to Kikuyu gr ass antigens were oberved. In 29/43 patients, IgE bound to two dominan t 48 and 70 kD allergens in the Kikuyu extract. Although a degree of c ross-reactivity with Bermuda grass (Cynodon dactylis) was found in imm unoabsorption studies, the 48 and 70 kD allergens appear to be unique to Kikuyu grass. Exposure of heparinized blood from Kikuyu grass-posit ive patients to the Kikuyu extract stimulated the release of histamine from their basophils in vitro. Kikuyu grass pollen is thus identified as an important aero-allergen in South Africa.