Mouse Anti-IgM Hybridoma [6D0]

It is well known that older people are more susceptible to morbidity and mortality from infectious diseases, particularly from pulmonary diseases such as pneumococcal pneumonia where vaccines do not provide efficient protection as in younger populations. We have previously shown that the B-cell repertoire in the old is reduced and hypothesise that this may contribute to the impaired humoral responses of the elderly. Here, we investigated the repertoire and antibody responses to winter vaccination in two age groups, aged 1849 and 6589. We found that the serum IgM and IgA pneumococcal responses were significantly impaired in the older group, with no difference in IgG levels. IGHM spectratype analysis seems to be the most promising in terms of its predictive ability for vaccine responses. Spectratypes showed a clear change in the repertoire at day 7 after vaccination, with a return to the baseline levels at day 28. The changes at day 7 reflected expansion of IGH sequences that have smaller, more hydrophilic, CDR3 regions, and these changes were attenuated in the older group. The older group was more likely to have spectratypes indicative of a reduced diversity at day 0 and day 28. On average, the baseline repertoire in the older group was comprised of larger CDR3 regions than in the younger group. In conclusion, IgA and IgM responses are significantly impaired in the elderly pneumococcal response and are likely key mediators of protection. Hydrophilicity and/or small size of the IGH CDR3 appear to be important in these responses.

The protein Zfp318 is expressed during the transition of naive B cells from an immature to mature state. To evaluate its role in mature B cell functions, a conditional gene deficiency in Zfp318 was created and deleted in bone marrow lineages via Vav-Cre. B cell development was minimally altered in the absence of the protein, although transitional 2 (T2) B cell populations were depressed in the absence of Zfp318. Intriguingly, the analysis of IgM and IgD expression by maturing and mature naive B cells demonstrated an elevated level of IgM gene products and a virtual loss of IgD products. Transcriptome analysis of Zfp318-deficient B cells revealed that only two gene products showed altered expression in the absence of Zfp318 (Ighd and Sva), demonstrating a remarkable specificity of Zfp318 action. In the absence of Zfp318, Ighm/Ighd transcripts, which would normally encode IgM and IgD from heterogeneous nuclear RNA transcripts via alternative splicing, lack intron and exon sequences from the IgD (Ighd)-encoding region. This finding indicates that Zfp318, in a novel manner, functions by repressing recognition of the transcriptional termination site at the 3' end of the terminal IgM-encoding exon, allowing for synthesis of the complete Ighm/Ighd heterogeneous nuclear RNA.