Anti-IgM Anticorps [MT6A3] (A269915)

Mice deficient in central components of classical NF-?B signaling have low levels of circulating natural IgM antibodies and fail to respond to immunization with T-independent type 2 (TI-2) antigens. A plausible explanation for these defects is the severely reduced numbers of B-1 and marginal zone B (MZB) cells in such mice. By using an ethyl-N-nitrosourea mutagenesis screen, we identified a role for the atypical I?B protein I?BNS in humoral immunity. I?BNS-deficient mice lack B-1 cells and have severely reduced numbers of MZB cells, and thus resemble several other strains with defects in classical NF-?B signaling. We analyzed mice heterozygous for the identified I?BNS mutation and demonstrate that these mice have an intermediary phenotype in terms of levels of circulating IgM antibodies and responses to TI-2 antigens. However, in contrast to mice that are homozygous for the I?BNS mutation, the heterozygous mice had normal frequencies of B-1 and MZB cells. These results suggest that there is a requirement for I?BNS expression from two functional alleles for maintaining normal levels of circulating natural IgM antibodies and responses to TI-2 antigens.

Neutralizing Abs provide the protective effect of the majority of existing human vaccines. For a prophylactic vaccine against HIV-1, broadly neutralizing Abs targeting conserved epitopes of the viral envelope glycoproteins (Env) are likely required, because the pool of circulating HIV-1 variants is extremely diverse. The failure to efficiently induce broadly neutralizing Abs by vaccination may be due to the use of suboptimal immunogens or immunization regimens, or it may indicate that B cells specific for broadly neutralizing Env determinants are selected against during peripheral checkpoints, either before or after Ag encounter. To investigate whether perturbation of B cell subsets prior to immunization with recombinant Env protein affects the vaccine-induced Ab response in mice, we used B lymphocyte stimulator (BLyS), a cytokine that regulates survival and selection of peripheral B cells. We show that the transient BLyS treatment used in this study substantially affected naive B cell populations; in particular, it resulted in more B cells surviving counter-selection at the transitional stages. We also observed more mature naive B cells, especially marginal zone B cells, in BLyS-treated mice. Intriguingly, provision of excess BLyS prior to immunization led to a consistent improvement in the frequency and potency of HIV-1 Env vaccine-induced neutralizing Ab responses, without increasing the number of Env-specific Ab-secreting cells or the Ab-binding titers measured after boosting. The results presented in this article suggest that an increased understanding of BLyS-regulated processes may help the design of vaccine regimens aimed at eliciting improved neutralizing Ab responses against HIV-1.