Plasma proenkephalin peptide F and human B cell responses to exercise stress in fit and unfit women.

In vitro studies have connected immune cell function to Peptide F. The primary purpose of this investigation was to examine the responses of plasma Peptide F and epinephrine along with the changes in B cell antibody production in vivo in physically fit and unfit women in response to physical exercise on a cycle ergometer at 60% and 80% of peak oxygen consumption. Seven aerobically fit and eight untrained (i.e., unfit) women between the ages of 18 and 30 volunteered to participate in this investigation. Blood samples (analyzed for plasma Peptide F and epinephrine along with the number of antibody-producing B cells) were obtained 24 hours prior to the exercise session, pre-exercise, during each exercise intensity, and five minutes post-exercise. The fit group had a significantly higher plasma Peptide F concentration after the 80% exercise intensity along with significantly higher numbers of antibody producing B cells compared to the unfit group. The results of this investigation show that physically fit women have an enhanced secondary response of B cells to a specific antigen under conditions where Peptide F is increased. Such data demonstrate that physical fitness as promoted by the Public Health Service (e.g., Healthy People 2000) influences the underlying hormonal and immune cell responses when challenged by physical exercise stress.