Enhancement in Igha mouse strains of the “natural” suppressive activity of normal T splenocytes against the expression of Igh-1b allotype. I. Molecular aspects of the chronic suppression obtained

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Abstract
Several approaches have been used in our attempts to increase the “natural” ability of normal T splenocytes (Tn) from BALB/c or BC8 mice (both Igha ) to induce, in F1 hybrids, a suppression of Igh-lb expression (IgG2a of b haplotype). These heterozygous F1 were produced by mating these Igha mice and their Ighb-congenic partners (CB20 and C57BL/6, respectively). The most powerful approaches were to sensitize the Igha mice by either autologous splenocytes coated with Igh-lb or B splenocytes from Ighb-congenic mice. In F1 having paternally inherited the b haplotype the sensitized T splenocytes (Tn) prepared from such mice are able to induce, like Tn when injected at birth, a chronic suppression of Igh-lb expression. However, the suppression was established with a much higher efficiency: already at 6 weeks of age in 100% of the F1 treated with 1 × 107 Ts vs. a final rate of 70% progressively reached only at 42 weeks of age in the F1 treated with 4 × 107 Ts. In F1 having maternally inherited Ighb the differences were even more pronounced than with 4 × 107 Tn i.e. the suppression induction was almost totally ineffective, whereas with 2 × 107−4 × 107 Ts a rate of 100% treated F1 subjected to suppression was reached at 19 weeks of age. As the productions of IgM, IgD and IgA of the b haplotype were not affected by the suppression, the Ts are believed to act on the Igh-lb′ cells. Attempts were also made to induce allotypic suppression of other b allotypes by the use, as sensitizing cells, of myeloma cells carrying Igh-6b (IgM of b haplotype). We failed in revealing any sign of a T cell reactivity against Igh-6b similar to the reactivity against Igh-lb. The use of Igh-6b+ myeloma cells grown in an Igh′ or in an Igha background allowed us to assume that the cells responsible for the sensitization are, in the Ighb B lymphocyte population, either the Igh-lb+ lymphocytes or the lymphocytes having passively adsorbed this allotype, or both.