Suppression of the primary IgM response by environmental teichoic acid

It has been shown previously that ingestion of glycerol teichoic acid (GTA) in the conventional laboratory diet (8 mg/kg) is the stimulus for natural background responses to GTA in rats. Since injected GTA suppresses responses to sheep red blood cells (SRBC), it was suspected that dietary GTA also might be acting suppressively. A comparison of rats fed the conventional diet with rats fed a GTA-free diet showed that ingested GTA markedly suppressed immune and background direct plaque-forming cell (PFC) responses to SRBC. It appeared that a direct causal relationship existed between the degree of suppression and the amount of GTA exposure. When GTA-deprived rats were force-fed varying doses of GTA or when conventional animals were injected (i.p.) with GTA, increasing the total GTA dose resulted in decreased direct PFC responses to SRBC. Suppression was also observed when GTA-deprived rats were force-fed GTA-containing Bacillus sp. ATCC 29726. The phenomenon of suppression by dietary GTA was not restricted to responses to SRBC, as similar results were obtained with chicken erythrocytes. When IgG PFC were measured, no difference between conventional and GTA-deprived groups was observed. Thus, an IgM-IgG shift does not seem to play a role in the mechanism of suppression by GTA.