Masako Fujita

The immune system of milk (ISOM) protects infants against infectious disease. However, immune protection trades off with potential immune-mediated harm, with immune protection coming at the risk of collateral damage to unintended targets like beneficial microbes or self-tissues. An evolutionary perspective suggests that the ISOM should be selected to be competent in differentiating pathogenic from benign targets. However, both protective immune responses and control of immune damage are energetically costly, nesting this tradeoff in a larger set of tradeoffs between maternal reproduction and immune function. This project investigates whether and how chronic stressors (which drain maternal biological resources) may affect ISOM competence, which we call “milk immune specificity.” We will evaluate whether chronic stressors (environmental, nutritional, and psychosocial) disrupt the balance between appropriate and inappropriate milk immune activity, using in vitro milk stimulation, which captures pro-inflammatory activity in the presence of bacteria. We will characterize milk in vitro interleukin-6 (IL-6) responses to Salmonella enterica (pathogenic) and Bifidobacterium breve (benign/beneficial) among mother-infant dyads in Michigan, USA. Regression models will evaluate stressors as predictors of IL-6 responses. The results will advance ecological understanding of ISOM activity and reproduction-immune tradeoffs inherent in human life history, focusing on maternal stress.