In order to investigate an effects of the hot spring within a short period on immune system of human, the leukocyte, monocytes, lymphocyte and lymphocyte surface markers: CD2, CD4, CD8, CD16, CD19 and CD57 were tested in the human peripheral blood of twenty-three healthy volunteers by hot spring bathing. The results were as follows: Total number of leukocytes and lymphocytes in the peripheral blood significantly increased in an older group after hot spring bathing (p<0.01). However, we obtained a clear decrease in the number of granulocyte after hot spring bathing in the younger group (p<0.01). In addition, we found greater increase of the CD16⁺ cell counts and a clear decrease of the CD19⁺ cell counts in older group. But in younger group, we also obtained an increase of CD8⁺, CD16⁺ cells after hot spring bathing. These results indicated that hot spring bathing can regulate the physical immune system.
According to the percentage of lymphocytes or granulocytes in the total leukocytes, volunteers were divided into two types, more than 70% of granulocyte were recognized as G type and more than 40% of lymphocyte were divided in the L type. We found an increase of lymphocyte and lymphocyte subsets as well as a decrease in granulocyte in G group by hot spring bathing. But in L group, especially, indicated a greater increase in granulocyte and a decrease in lymphocyte subsets. We suggest that hot sping bathing can regulate by an autonomic nerve system, making it suitable.

We have simultaneously proved that cell populations taking charge of immunity in human peripheral blood can be regulated quantitatively by hot spring bathing. Now, we investigated the effect of hot spring bathing qualitatively on cytokine production by lymphocyte cell in human peripheral blood estimating by cytokine containing cell by FACScan. We found a significant increase in IFN-γ containing cells after hot spring bathing and an increase in IL-4 with no statistical significance after hot spring bathing. In addition, we found significant negative relationship between the level of IFN-γ, IL-4 and IL-1β before hot spring bathing and the ratio of cytokine that increased in variation after hot spring bathing. Namely, after hot spring bathing, there was a decrease of cytokine producing cells in subjects who had higher level before hot spring bathing. But an increase in subjects who had lower level before hot spring bathing, the trend was concentrated toward average levels in the cytokine production by lymphocyte in peripheral blood. So we suggest that hot spring bathing can promote acquired immunity to make it possible more suitable as immune reaction.