Summary:An in utero paternal CD34+ cell transplant was performed in a T-B+NK+ SCID fetus. We report here the results of the 3-year humoral immune reconstitution study. The methods used were ApoB VNTR typing, flow cytometry, nephelometry, hemagglutination, ELISA, ELISPOT and lymphoproliferative assays. The T cells were of donor origin whereas monocytes, B and NK cells were of host origin. Peripheral B cell counts and IgM levels were normal since birth. IVIG therapy was required at 5 months of age until 2 years old. IgA levels у20 mg/dl were detected from month 17 post transplantation. Isohemagglutinins were present since month 8 post transplantation, the highest titers + BM cell transplantation, we and others have previously demonstrated lymphoid engraftment and restoration of T cell function early after in utero BMT.2-4 However, there is limited information on the long-term immune reconstitution, mainly on humoral immune responses in patients with SCID and in utero BMT. normal B cell function requires T-B cell co-operation and it is delayed when compared to T cell reconstitution. Full restoration of B cell function is achieved in 60-70% of B+ SCID patients only several years after HLA haploidentical T cell-depleted BMT. 5 The lack of adequate levels of serum Igs in those patients who do not achieve B cell reconstitution requires IVIG treatment.In this study, we present data of the 3-year follow-up on B cell reconstitution in one SCID patient who was treated with in utero haploidentical BMT. Materials and methods PatientImmunological analyses which were performed prior to and immediately after in utero BMT are described elsewhere. 4 Briefly, in September 1997, a T-B+NK+ SCID prenatal diagnosis was performed on a male fetus at week 23 of gestation. The parents were related and they had a previously affected T-B+NK+ SCID son (unknown molecular etiology). Paternal BM CD34 + cells were purified and two i.p injections (the second infusion together with ex vivo generated BM stromal cells) were performed in the Spedali Civili, Brescia, Italy. 4 The donor did not have antibodies to hepatitis B virus (HBV) and he had never been vaccinated against HBV. The T cell function in the patient developed at month 4 post transplantation and it has remained normal since then. Serum IgG levels progressively fell within the first months of life, IVIG therapy (400 mg/kg every 4 weeks, Endobulin IV; Baxter, Vienna, Austria) was started when IgG levels dropped below 200 mg/dl (Figure 1). The patient's growth and development have always been normal. He has presented several upper respiratory infections, two episodes of gastroenteritis and two episodes of otitis media. The patient received prophylaxis with ketoconazole, acyclovir and co-trimoxazole until he was 6 months old. He has completed the following vaccination schedule: HB, DTP, Hib and eIPV immunizations were administered at 3 months of age; HB and eIPV at 4 months of age, DT, Hib and eIPV at 6 months of age, HB and meningococcal A+C vaccine when he was 1 year old, and DT and Hib a...

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