The closed antibody is a mixed antibody, present in the serum of normal pregnant women, which closes off the cytotoxic effect of maternal lymphocytes on the trophoblast of the embryo and prevents the mother’s immune system from attacking the embryo. If the embryo is compared to a vegetable, the closed antibody can be seen as a vegetable trellis, with the protective effect of the trellis, the vegetable can resist the attack of external adverse factors. However, 80-90% of women with habitual miscarriage do not have this specific closed antibody, and there are uninhibited cytotoxic cells in the body, which can act directly on the embryo or indirectly damage the fetus or placenta through the release of inflammatory mediators, thus leading to miscarriage. Therefore, closed antibody negativity is one of the adverse factors for patients with recurrent miscarriage and needs to be treated. For these patients, the goal of treatment is to induce maternal production of closed antibody. Currently, our department uses leukocyte immunotherapy, in which 20-30 ml of venous blood from the husband or a healthy third party (an unrelated healthy male of the patient’s own choosing) is drawn, and after anticoagulation, leukocytes are made into a suspension and injected into the patient on the same day. When the patient is found to be positive for closed antibodies after one stage of treatment, conception can be arranged and the immunization is reinforced at different times during the pregnancy until after the sixth month of pregnancy.