The immune response deficiencies in patients with stages I and IIA breast cancer, with primary surgical treatment, highlighted in this study are: impaired functionality of Th lymphocytes and increased immunosuppression, evidenced by the drop in IL-2 production (p<0.01); reverse correlation between lymphocytic function alteration and bcl-2 protein expression confirm the poor apoptotic activity of tumour cells (p<0,02); alteration of the lymphocytic function supported by the change in the I.PHA/I.ConA ratio associates with a tumour diameter greater than 2 cm (p<0.02). The gene discussed is BCL2; the disease is neoplasm.