Influence of a V kappa 8 L chain transgene on endogenous rearrangements and the immune response to the HA(Sb) determinant on influenza virus

A rearranged murine V kappa 8/J kappa 5 L chain gene that codes for the L chain of most antibodies generated in the primary response of BALB/c mice to the antigenic site, Sb, of the hemagglutinin (HA) molecule of influenza virus A/PR/8/34 (PR8) has been cloned. Three transgenic lines were generated by microinjecting the gene. Lines Ga and L each contain a single copy of the transgene whereas line Gb contains three complete copies. Mice of the Ga lineage showed increased V kappa 8-specific mRNA levels only in spleen, but not in nonlymphoid organs and therefore displayed apparently normal lymphoid-specific regulation of the Ig transgene. B cell hybridomas generated from these mice were analyzed for rearrangements of endogenous V kappa genes. Greater than 90% of the C kappa alleles were retained in germ-line configuration in the Ga line, compared with only 0 to 18% in the L line. Thus, a wide variation in the frequency of endogenous rearrangements is seen among mice of different lineages using the same transgene construct. None of more than 150 hybridomas derived from LPS-stimulated splenic B cells of Ga mice exhibited HA-binding activity although they expressed the transgene and, in most cases, excluded endogenous V kappa rearrangements. In contrast, a large fraction of hybridomas isolated after primary immunization with PR8 were HA(Sb)-specific. This indicated that the transgene was functional but formed HA-specific antibodies with a more restricted set of H chains than previously hypothesized. The primary anti-HA response to immunization with PR8 was diminished in all lines compared with normal mice except for a slightly accelerated but transient burst of anti-HA antibody formation in two out of three lines (Ga and Gb). This early response in G lineage mice was largely specific for HA(Sb) and thus appeared to be composed of transgene-expressing antibodies. No differences in serum titers were observed in the secondary anti-HA responses to booster inoculation with PR8 between transgenic and normal mice.