Pre-existing CD4 T cell help boosts antibody responses but has limited impact on germinal center, antigen-specific B cell frequencies after influenza infection.

The influenza virus is a persistent burden on global health, with seasonal vaccines providing incomplete protection. CD4+ T cells help shape B cell and antibody responses; however, the selectivity of help and the effect on various antigen-specific B cell populations have not been fully elucidated. Here, we studied the specificity, selectivity, and influence of nucleoprotein (NP) CD4+ T cells on the magnitude and quality of hemagglutinin (HA) and NP-specific B cells and antibody responses. We identified immunodominant peptides and showed that peptide immunization was sufficient to induce CD4+ cells with Th1 and Tfh phenotypes. Surprisingly, while preexisting CD4+ T cells enhanced the influx of total germinal center (GC) B cells in the mediastinal lymph node after infection, this was not reflected by an increase in the frequency of antigen-specific cells within the GC. Furthermore, we demonstrated that NP-specific help was able to accelerate the kinetics and magnitude of the Ab response for NP but not for HA. Overall, our results showed that pre-existing CD4+ T cells provide strong cognate help during immunization or infection to enhance Ab production but not antigen-specific GC or memory B cells.

Memory B-cell diversity: From early generation to tissue residency and reactivation.

Memory B cells (MBCs) have a crucial function in providing an enhanced response to repeated infections. Upon antigen encounter, MBC can either rapidly differentiate to antibody secreting cells or enter germinal centers (GC) to further diversify and affinity mature. Understanding how and when MBC are formed, where they reside and how they select their fate upon reactivation has profound implications for designing strategies to improve targeted, next-generation vaccines. Recent studies have crystallized much of our knowledge on MBC but also reported several surprising discoveries and gaps in our current understanding. Here, we review the latest advancements in the field and highlight current unknowns. In particular, we focus on timing and cues leading to MBC generation before and during the GC reaction, discuss how MBC become resident in mucosal tissues, and finally, provide an overview of factors shaping MBC fate-decision upon reactivation in mucosal and lymphoid tissues.

Myokines and Resistance Training: A Narrative Review.

In the last few years, the muscular system has gained attention due to the discovery of the muscle-secretome and its high potency for retaining or regaining health. These cytokines, described as myokines, released by the working muscle, are involved in anti-inflammatory, metabolic and immunological processes. These are able to influence human health in a positive way and are a target of research in metabolic diseases, cancer, neurological diseases, and other non-communicable diseases. Therefore, different types of exercise training were investigated in the last few years to find associations between exercise, myokines and their effects on human health. Particularly, resistance training turned out to be a powerful stimulus to enhance myokine release. As there are different types of resistance training, different myokines are stimulated, depending on the mode of training. This narrative review gives an overview about resistance training and how it can be utilized to stimulate myokine production in order to gain a certain health effect. Finally, the question of why resistance training is an important key regulator in human health will be discussed.