IGE RECEPTOR EXPRESSION AND IGE CONTENT ON MAST-CELLS OF NORMAL, GROWING RATS

A cytofluorometric method was used to measure the number of IgE recept ors available for binding and the native IgE content on microscopicall y identified peritoneal mast cells of Sprague-Dawley rats age 4 to 5 w eeks. During this period of growth, the mast cells increased progressi vely in size, granule mass and histamine content, but the number of Ig E receptors did not increase in relation to body weight or age, althou gh it varied greatly within the mast cell populations of individual ra ts as well as between the different rats. The peritoneal mast cells of these normal, naive, specific pathogen-free rats raised under control led conditions and without sips of infections, were found to carry a s ignificant number of IgE molecules of unknown specificity. The IgE con tent varied greatly among the individual mast cells within a given pop ulation, but, on average, as much as 74 % of the receptors available f or binding were occupied.