Abstract
We examined the specificity of the recently reported alterations in circulating lymphocytes in heatstroke by determining lymphocyte subsets in 14 consecutive heatstroke patients before and after cooling and in 7 heat-stressed controls using single- or two-color immunofluorescence flow cytometry. The relationship with catecholamine levels was also studied. In heatstroke, percentages of T (CD3
+
/CD19
−
), T-helper (CD4
+
/CD8
−
), T-inactive [CD3
+
/human leukocyte antigen-DR
−
], CD11a
+
, CD11c
+
, and CD44
+
lymphocytes were significantly decreased, whereas percentages of T-suppressor-cytotoxic (CD8
+
/CD4
−
), natural killer (NK; CD3
−
/CD16
+
or CD56
+
), CD3
+
/CD16
+
or CD56
+
, and CD54
+
lymphocytes were significantly increased, compared with 11 normal controls. The changes in the absolute numbers of lymphocyte subsets were in the same direction and were significant for T-helper, T-suppressor-cytotoxic, NK, CD3
+
/CD16
+
or CD56
+
, and CD11c
+
lymphocytes. Milder but significant changes in percentages of T-helper, T-suppressor-cytotoxic, CD11c
+
, and CD44
+
lymphocytes were seen in heat stress. Cooling was associated with partial or complete normalization, further derangement (CD11a
+
, CD11c
+
), or overcorrection (NK, T-suppressor-cytotoxic, CD11b
+
) of abnormal percentages of lymphocyte subsets. Norepinephrine levels were significantly elevated in heatstroke (4.7-fold) and heat stress (3.2-fold), but did not significantly correlate with lymphocyte subsets. We conclude that heatstroke is associated with significant changes in percentages and in absolute numbers of a wide range of circulating lymphocyte subsets that are not related to elevated catecholamine levels or totally normalized by cooling. Similar, albeit milder, changes are seen in heat stress, suggesting that the two syndromes represent a continuum.