Immunity to Salmonella gallinarum during ontogeny of the chicken. II. Induction of tolerance or priming by single doses of live or killed bacteria.

Partial tolerance was induced in cells forming agglutinins by live or killed, virulent or avirulent strains of in chick embryos, 1-day and 1-week-old chicks. Tolerance was induced by a single injection of only 100–200 live virulent organisms in 1-day-old and 1-week-old chicks. However, 10 avirulent organisms were required to induce a similar degree of tolerance in 1-week-old chicks. The primary agglutinin response paralleled the relative increase in spleen weight during early development and increased only slightly after 5 weeks of age. Priming to live bacteria occurred at 2 weeks of age; the magnitude of the secondary response showed little further increase with age. The induction of partial tolerance in cells producing agglutinins did not increase susceptibility to infection and further emphasizes that agglutinin production is not a protective immune mechanism for infection.