Heat shock proteins (HSPs) are present in neutrophils (PMNs) from critically ill patients. We investigated whether HSPs were present in PMNs from burn patients and whether heat shock contributed to the functional defects observed in burn PMNs. Using both flow cytometry and Western blot techniques it was observed that inducible HSP72 (iHSP72) was present in PMNs and leukocytes from burn patients, especially in patients with inhalation injury. Similar to burn PMNs, and in contrast to normal cells, heat shocked PMNs (43 degrees C incubation) expressed iHSP72 and were unable to increase the expression of CD11b/CD18 in response to pro-inflammatory stimuli. Degranulation after pro-inflammatory stimuli was decreased for both burn- and heat-shocked PMNs when compared to normal controls. In burn PMNs these functional abnormalities were mainly due to decreased quantities of proteins (CD11b, albumin, B12 binding protein, beta-glucuronidase) present within cytoplasmic granules. However, in heat-shocked PMNs the abnormalities were primarily related to abnormal exocytosis. In conclusion, our data show that decreased quantities of cytoplasmic granule proteins and, to a smaller degree, defective exocytosis are involved in the functional abnormalities observed in burn PMNs.