**Abstract**

The spleen is the largest peripheral organ of the immune system. The standard volume of lymphodissection in stomach cancer during gastrectomy or proximal resection is D2, which implies splenectomy. Immunity disorders in patients after splenectomy primarily affect the B cell immune response. Peripheral blood B-lymphocytes subpopulations have been studied in patients with gastric cancer. Group 1 - patients with gastrectomy, D2 lymphodissection, group 2 - patients with gastrectomy, D2-lymphodissection, splenectomy. Evaluation of the expression of antigens (CD20, CD21, CD23, CD38, HLA-DR, CD71, CD10, CD95, CD25, CD5, CD56, κ- and λ-light was performed in the gate of CD19+ cells. Among peripheral blood lymphocytes the presence of CD19+CD5+ B cells (B1a cells), some of which express the activation antigens CD38 and CD23 is found; a small part of CD5+ B cells is CD25+CD38−. The number of CD23+ cells ranged from 25 to 40% in different patients. A significant number of B cells with a low level of CD21+ expression were detected. In group 2 after surgery, the percentage of cells with CD5+ expression significantly increased, the relative amount of CD19+ lymphocytes, CD19+CD21+ B cells decreased. Given data on B1 and BMZ populations, this can lead to a weakening of both general and antitumor immunity.

**Keywords:** B lymphocytes, B1 cell, cells of the marginal zone of the spleen, thymus-independent antigens, humoral immunity, stomach cancer, splenectomy, splenomegaly, D2 lymphodissection, IgM
