Effects of hyperthermia on spectrin expression patterns of murine lymphocytes.

In this study the influence of whole-body hyperthermia on the distribution of spectrin in murine lymphocytes isolated from various lymphoid tissues is examined. Lymphocytes normally vary in terms of the pattern of spectrin distribution within the cell. In certain populations of lymphocytes, spectrin is distributed into a dense submembranous aggregate that can be easily identified by immunofluorescence microscopy. In these lymphocytes, little or no spectrin is seen at the plasma membrane region in the rest of the cell. Other lymphocytes have no such cytoplasmic aggregates, and the protein is seen at the region of the plasma membrane. Following whole-body hyperthermia (40.5 degrees C for 90 min) there is a 100% increase in cells exhibiting polar spectrin aggregates in the spleen, while lymphocytes from the thymus show no alteration in the number of cells showing such aggregates. The increase in the percentage of splenic cells that express aggregated spectrin is a result of increases occurring in both T- and B-cell subsets. This increase gradually returns to control levels by 48 h post-heating. During recovery to control levels this phenomenon is resistant to additional changes when a second heat treatment is applied. The effects described above are not observed when the experiments are performed in vitro; therefore, it is likely that the in vivo heat-induced alteration in the splenic lymphocyte population reflects the physiological response of lymphocytes to stimuli during a natural fever. The role that spectrin may play in the modulation of lymphocyte membrane properties is discussed.