Upon vaccination, B cells differentiate into antibody secreting cells (ASCs) that migrate via the circulation to tissues. The kinetics of this response and the relationship of circulating ASCs to protective antibody titers have not been completely explored.Methods-Influenza-specific and total-IgG ASCs were enumerated by Elispot and flow cytometry daily in the blood in 6 healthy adults after trivalent influenza vaccination (TIV).Results-Peak H1-specific IgG ASC frequencies occurred variably from day 5 to 8 and correlated with the fold-rise rise in hemagglutination inhibition (HAI titers); r=0.91, p=0.006. H3-specific IgG ASC frequencies correlated less well, perhaps due to a mismatch of the H3 protein in the vaccine and that used in the Elispot assay. Peak frequencies of vaccine-specific and total-IgG ASCs were 0.3% and 0.8%, respectively, of peripheral blood mononuclear cells (PBMC). Peak TIV-, H1-, H3-, and total-IgG ASC frequencies were 1736 ± 1133, 626 ± 520, 592 ± 463, and 4091 ± 2019 spots/10 6 PBMC, respectively. Peak TIV-, H1-, and H3-specific IgG ASC of totalIgG ASC frequencies constituted 63% ± 21, 26% ± 10, 22% ± 17, respectively. Conclusion-After immunization with inactivated influenza vaccine the peak in influenzaspecific ASC frequencies is variable but correlates well with the magnitude of protective HAI responses.

No abstract

Native human Abs represent attractive drug candidates; however, the low frequency of B cells expressing high-quality Abs has posed a barrier to discovery. Using a novel single-cell phenotyping technology, we have overcome this barrier to discover human Abs targeting the conserved but poorly immunogenic central motif of respiratory syncytial virus (RSV) G protein. For the entire cohort of 24 subjects with recent RSV infection, B cells producing Abs meeting these stringent specificity criteria were rare, <10 per million. Several of the newly cloned Abs bind to the RSV G protein central conserved motif with very high affinity (Kd 1–24 pM). Two of the Abs were characterized in detail and compared with palivizumab, a humanized mAb against the RSV F protein. Relative to palivizumab, the anti-G Abs showed improved viral neutralization potency in vitro and enhanced reduction of infectious virus in a prophylaxis mouse model. Furthermore, in a mouse model for postinfection treatment, both anti-G Abs were significantly more effective than palivizumab at reducing viral load. The combination of activity in mouse models for both prophylaxis and treatment makes these high-affinity human-derived Abs promising candidates for human clinical testing.

Although T cell effector subsets, defined by cytokine patterns, have been recognized for more than 20 years, the functional cytokine expression patterns in vivo are still in considerable doubt, particularly for human T cells. At least three new subsets have been recently identified, but the committed cytokine pattern of a T cell (e.g., Th1 cells produce IL-2, interferon-gamma, and lymphotoxin) may differ from the expression pattern of one cell on one occasion, which may be a subset of its full potential. Recent advances in flow cytometry allowed detailed cytokine patterns of antigen-stimulated cells to be identified directly ex vivo. These patterns are clearly more diverse than the major subsets identified as committed phenotypes. Additional contributions to diversity may include new committed subsets, random expression of only part of the committed pattern, and modification of the expression patterns by cytokines and other mediators.

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In this issue, Milovanovic and colleagues present evidence that IL-17a enhances IgE production, although the precise mechanism remains unclear. Their initial finding was that higher numbers of IL-17a-producing CD4(+) T cells were observed after polyclonal stimulation in a largely airway allergic population. These data add to the evidence that atopic disorders such as asthma and, possibly, atopic dermatitis (AD) may have distinct immunologic phenotypes. The hope is that by characterizing the immunologic basis of these common diseases we will be able to understand the heterogeneity observed in natural history, response to treatments, susceptibility to infections, genetic risk factors, and associations with other atopic disorders.