Pollen-white cell interactions

Abstract

One of the early interactions in vitro of white cells (except lymphocytes) with low ragweed pollen grains is the adherence of white cells to pollen grains. This is augmented by sera from either normal and sensitized guinea pigs or normal and atopic human subjects. Two morphologically distinct shapes of adhering white cells are evident. These consist of round and crescent-shaped white cells. Most white cells which adhere to low and giant ragweed pollen grains are round. In contrast, most white cells which adhere, in the presence of serum, to pollen grains of other species or to defatted low ragweed pollen grains are crescent shaped. Adherence is optimal under physiologic conditions, requires viable white cells, and is inhibited by glycolytic poisons. The factor or factors in the serum (pollen adherence factor[s]: PAF) which augment the adherence of white cells to pollen grains are significantly increased in sera of guinea pigs which have been previously injected with low ragweed pollen grains in Freund's complete adjuvant. PAF have been selectively removed by absorption with whole ragweed pollen grains. Antibodies to sheep red cells, skin-sensitizing antibodies, dialysis of serum, and low ragweed extracts do not significantly affect PAF activity. Heat inactivation of serum diminishes but does not stop PAF activity. The initial interactions of white cells with pollen grains in vivo, upon intraperitoneal injection of pollen, are similar to those which occur in vitro.