Ontogeny of cells involved in the suppressor circuit of the immune response.

Some macrophage (M phi) cell surface structures which bind T cell-derived factors remain intact after the M phi are killed by heating at 56 degrees C (but not 72 degrees C) for 45 min. As a result, appropriately killed M phi (HK M phi) can act as competitive antagonists for those M phi functions which are involved in binding and active presentation of T cell-derived regulatory signals. By blocking the transmission of these signals with HK M phi, we have found that the spleens of newborn mice contain considerable numbers of "latent" helper cells whose activity is not ordinarily seen because it is overridden by suppressor mechanisms. Similarities between these neonatal helper cells and a subset of adult T helper "inducer" cells (cell surface phenotype Ly-1+; Ly-2-, 3-; IJ+; Qa 1+), whose activity appears in significant numbers only after immunization, are described.