What is a closed antibody (BA)? Modern immunology considers pregnancy to be a successful semi-identical transplantation process, and BA is a variety of IgG-type antibodies produced by the mother in recognition of the fetus’ paternally derived human leukocyte antigens (HLA) and placental trophoblast lymphocyte cross-antigens, among others. By blocking the antigens of fetal and placental tissues from maternal immune rejection, the pregnancy is maintained. And if the mother fails to produce BA in a timely and effective manner, it can lead to a variety of adverse pregnancy outcomes such as early miscarriage and embryonic abortion. Simply put, the baby is the fruit of the mother and father, and the role of BA is to prevent the mother’s organism from harming the baby by recognizing the paternal antigen. Because of the long half-life of IgG-type antibodies, BA is not only present only in the serum of pregnant women, and the rate of BA positivity increases with the number of pregnancies. BA test is suitable for 1. patients with recurrent spontaneous abortion (RSA, 2 or more spontaneous abortions) and embryonic abortion; 2. hysteroscopy or ultrasound to rule out anomalies in uterine anatomy; 3. basal body temperature or luteal phase progesterone measurement without abnormal luteal function; 4. negative TORCH 4 IgM, negative cervical secretions for mycoplasma and chlamydia; 5. anti-cardiolipin antibodies, anti-nuclear antibodies, anti anti-sperm antibodies, anti-endometrial antibodies, anti-ovarian antibodies, and negative anti-trophoblast antibodies. Treatment of lymphocyte active immunotherapy for BA deficiency RSA Patients are treated with subcutaneous or intradermal injections of husband or third-party lymphocytes to actively induce closed antibody production.2 The efficacy of lymphocyte active immunotherapy for RSA has been confirmed in recent years, with an efficiency of 70%-90% reported in domestic and international literature. How to choose the blood donor 1. The patient’s husband is preferred. If the patient’s husband cannot supply blood due to blood-borne diseases, healthy third-party lymphocytes can be used for treatment, with no difference in efficacy. Try to choose those who are not related to the patient, otherwise the effect is slightly worse. There is no standard active immunotherapy protocol, and the number of immunotherapy sessions and injection methods are not all the same in each center. The diagram below shows the general treatment flow. Cautions 1. treatment should be avoided during the woman’s menstrual period and should not be performed if either partner has a fever or cold; 2. each treatment requires the blood donor to come for blood sampling; 3. adverse reactions to treatment: local adverse reactions: local redness, inflammatory reactions, hyperpigmentation, etc.; systemic adverse reactions: hypothermia, allergic reactions, etc.; 4. do not scratch the injection site and keep it relatively sterile and dry.