To investigate the humoral and cellular immune responses in patients with acute brucellosis, and evaluate dynamic changes of regulatory T-lymphocytes (Foxp3⁺ Treg) in the peripheral blood of patients during treatment, in order to clarify the relationship between immunosuppression and the therapeutic effect in human brucellosis.

Sixty-five patients with brucellosis hospitalized at the Third Department of Infectious Diseases, Heilongjiang Agriculture and Reclamation Bureau General Hospital between July 2015 and November 2015 were included. Twenty-eight patients were treated with conventional therapy (group A: patients received 3 courses of treatment. Each lasted for 20 days with one-week interval), and 37 patients were treated with conventional therapy in combination with immunopotentiator (group B). Thirty healthy volunteers were enrolled as the controlled group. The ratio of CD3⁺ CD4⁺ Foxp3⁺ Treg cells in the peripheral blood of brucellosis patients were measured by flow cytometry (FCM) at the end of each course of treatment. Data in accordance with normal distribution were described as mean±standard deviation. Comparison between two groups was done by two sample t test. Comparison among multiple groups was performed by analysis of variance and SNK test. Data that did not fit the normal distribution were analyzed by multiple-sample nonparametric test.

After the first (20 d), second (50 d) and third course of treatment (80 d), the ratios of Foxp3⁺ Treg in the peripheral blood of 65 acute brucellosis patients were 2.83%, 3.77% and 4.03%, respectively, which were all significantly higher than control group (1.69%; t=5.97, 9.05 and 5.66, respectively, all P<0.01). At the end of the first course of treatment, the ratios of Foxp3⁺ Treg in group A and B showed no statistically difference (t=0.33, P>0.05), while those were both higher than control group (t=7.09 and 4.94, respectively; both P<0.01). At the end of the second course, the ratio of Foxp3⁺ Treg in group B was higher than group A (t=2.22, P<0.01), and both of them were higher than control group (t=10.79 and 7.25, respectively; both P<0.01). At the end of treatment, Foxp3⁺ Treg in group A was also significantly higher than the other two groups (t=6.02 and 6.45, respectively; both P<0.01).

In patients with acute brucellosis treated with the standard antibiosis treatment in combination with immunopotentiator, the ratio of Foxp3⁺ Tregs significantly increases and maintains at a high level, which suggests that extra immunopotentiator may be not helpful for the treatment of brucellosis at the very early stage.

Brucella; Brucellosis; Treatment; Flow-cytometric analysis; T-lymphocytes, regulatory; Foxp3