Histamine and Stress Responses of Lymphoid Tissues

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Abstract
To study the possible role of histamine in stress responses of lymphoid tissues, mice, intact or adrenalectomized, were injected with a colloidal irritant, endotoxin, or were subjected to tourniquet trauma. Mice were sacrificed after various intervals, thymus and mesenteric lymph node were removed, weighed and assayed for histidine decarboxylase activity. In thymus there was little or no activation of histidine decarboxylase and a loss of weight always occurred in intact mice. In lymph nodes, stimuli which activated histidine decarboxylase also increased weight. The weight changes in lymph nodes cannot be fully explained by effects of released glucocorticoids. In all experiments, however, weight changes correlate with glucocorticoid effects plus an additional stress factor, that is, the degree of activation of histidine decarboxylase (and hence histamine production) within the tissue. The available evidence supporting histamine as a factor in lymphoid tissue growth is discussed.