Serum factors in experimental nephrosis prevent lymphocyte stimulation.

A factor found in the serum of rats made nephrotic by a single administration of puromycin aminonucleoside (PA) has been shown to inhibit the blastogenic response of normal rat spleen cells when stimulated with either phytohaemagglutinin (PHA) or concanavalin A (Con A). Spleen cells removed from the nephrotic animals also exhibited a reduced capacity to incorporate thymidine when cultured with normal serum. This potent inhibitor was not cytocidal, and inhibition was not due to a lack of components essential for normal growth. Inhibition was not due to the excess of low density lipoproteins found in the nephrotic serum. Increasing mitogen concentrations in the presence of the nephrotic serum had little effect on inducing thymidine uptake by the normal spleen cells, while washing of the cells removed from the nephrotic animals appeared to partially overcome suppression of blastogenesis. The inhibitory factor was found to be less effective if the spleen cells had already been triggered by mitogen to undergo transformation in normal serum before the addition of the nephrotic serum.