Eosinophils are required to suppress Th2 responses in Peyer's patches during intestinal infection by nematodes.

Infections with enteric nematodes result in systemic type 2 helper T (Th2) responses, expansion of immunoglobulin (Ig)G1 antibodies, and eosinophilia. Eosinophils have a supportive role in mucosal Th2 induction during airway hyperreactivity. Whether eosinophils affect the local T-cell and antibody response in the gut-associated lymphoid tissue during enteric infections is unknown. We infected eosinophil-deficient ΔdblGATA-1 mice with the Th2-inducing small intestinal nematode Heligmosomoides polygyrus and found that parasite fecundity was decreased in the absence of eosinophils. A lack of eosinophils resulted in significantly augmented expression of GATA-3 and IL-4 by CD4+ T cells during acute infection, a finding strictly limited to Peyer's patches (PP). The increase in IL-4-producing cells in ΔdblGATA-1 mice was particularly evident within the CXCR5+PD-1+ T-follicular helper cell population and was associated with a switch of germinal centre B cells to IgG1 production and elevated serum IgG1 levels. In contrast, infected wild-type mice had a modest IgG1 response in the PP, whereas successfully maintaining a population of IgA+ germinal center B cells. Our results suggest a novel role for eosinophils during intestinal infection whereby they restrict IL-4 responses by follicular T helper cells and IgG1 class switching in the PP to ensure maintenance of local IgA production.

Obesity, weight loss, and health.

Obesity is a multifactorial, complicated condition or group of conditions that afflicts a growing number of people in the United States. Precise etiologies are not well understood, and both commercial and medical treatment programs are characterized by high rates of recidivism. A cultural preoccupation with slimness has created a huge industry serving millions of people who are attempting continually to reduce weight. Contradictory messages from professionals have led to confusion concerning the health implications of obesity and the potential risks of repeated dieting. This review summarizes the major areas of consensus and controversy concerning the health implications of obesity and weight loss and suggests directions for treatment that take into account the complex causes and consequences of obesity.