Feminine mice demonstrated more efficient germinal center reactions, including increased class switching and affinity maturation. on our Bnip3 understanding of how females generate superior antibody reactions against influenza viruses and how this informs vaccine design. KEYWORDS:biological response modifiers, humoral immunity, influenza, influenza vaccines, neutralizing antibodies == COMMENTARY == Influenza viruses remain a major public health problem and are a leading cause of respiratory infections, hospitalization, and deaths in the United States. While AMG2850 seasonal influenza vaccines provide modest safety against influenza viruses, host factors play an important part in how humans respond to illness. Importantly, sex remains probably one of the most important biological variables in determining how well humans respond to the vaccination and are protected from illness. Earlier data on immune reactions after vaccination shown that there are sex-related variations, with females generating superior immunity following vaccination (1,2). However, the mechanisms by which females generate improved reactions to vaccination remain ill-defined. Understanding how sex affects immunity is an important goal that may improve vaccine immunogenicity and performance. In the study by Ursin et al. (3), the authors investigated the breadth of the humoral immune response in woman versus male mice by using mutant influenza viruses. The authors found that female mice were better guarded against influenza viruses and generated a broader AMG2850 antibody response, both of which are linked to bigger and better germinal center reactions. Here, we discuss how these findings fit into and increase upon AMG2850 our current understanding of sex like a determinant of how females generate superior antibody reactions, with implications for improving vaccine performance across sexes. == FEMALES MOUNT A MORE ROBUST ANTIBODY RESPONSE == Sex has long been a determinant of how well healthy adult humans respond to vaccination, with females generating higher humoral and cellular immune reactions following vaccination with nearly every vaccine analyzed (4). This is due to the fact that females are more likely to generate a strong inflammatory response relative to males, which leads to more immune cell activation, antigen demonstration, and selection. This increase in inflammatory reactions is due in part to sex-related environmental factors, such as estrogen levels, as well as genetic factors, particularly the possession of two X chromosomes. Estrogen has been well recorded in regulating a variety of immune functions, including B and T cell development, cellular activation and trafficking, cytokine and chemokine production, and cellular survival (5), all of which can effect humoral immunity. Moreover, several important B cell-regulating genes are on the X chromosome, includingTlr7, which is frequently overexpressed in females due to incomplete inactivation of one X chromosome (6). Notably, Toll-like receptor 7 (TLR7) manifestation by B cells promotes IgG2c class switching and protecting humoral immunity against viruses (7,8). Ursin et al. recognized that females experienced improved IgG2c class switching relative to that in male mice. Collectively, the effects of estrogen and elevated TLR7 expression can lead to improved type 1 inflammatory cytokines, including type I interferons, and B cell activation and class switching to IgG2c. == FEMALES GENERATE BETTER GERMINAL CENTER Reactions == In the article, the authors found that females generated a greater germinal center response, leading to increased effectiveness of somatic hypermutation AMG2850 (3). These data suggested that not only do females induce a greater germinal center-derived antibody response, but also that this response is definitely qualitatively better. The observed phenotype could AMG2850 be due to both genetic and hormonal factors. First, a recent report showed that male B cells are poorly positioned within the B cell follicle inside a sex-dependent manner, leading to impaired humoral immunity against both foreign and self antigens (9). As a result, woman B cells are better situated to enter germinal centers and to become presented antigen. In addition, TLR7 stimulation can lead to more and better germinal center B cells, which can increase somatic hypermutations and affinity maturation (8). Although these mechanisms were not explored in the study by Ursin et al. (3), these data suggest that sex variations could lead to variations in germinal center reactions and B cell selection via sex-dependent environmental and genetic factors that regulate B cell placement and activation. == FEMALES PRODUCE A BROADER ANTIBODY RESPONSE == Perhaps the most important getting of the Ursin et al. study.