First use of thymus transplantation therapy for FOXN1 deficiency (nude/SCID): a report of 2 cases

Abstract

FOXN1 deficiency is a primary immunodeficiency characterized by athymia, alopecia totalis, and nail dystrophy. Two infants with FOXN1 deficiency were transplanted with cultured postnatal thymus tissue. Subject 1 presented with disseminated Bacillus Calmette-Guérin infection and oligoclonal T cells with no naive markers. Subject 2 had respiratory failure, human herpes virus 6 infection, cytopenias, and no circulating T cells. The subjects were given thymus transplants at 14 and 9 months of life, respectively. Subject 1 received immunosuppression before and for 10 months after transplantation. With follow up of 4.9 and 2.9 years, subjects 1 and 2 are well without infectious complications. The pretransplantation mycobacterial disease in subject 1 and cytopenias in subject 2 resolved. Subject 2 developed autoimmune thyroid disease 1.6 years after transplantation. Both subjects developed functional immunity. Subjects 1 and 2 have 1053/mm(3) and 1232/mm(3) CD3(+) cells, 647/mm(3) and 868/mm(3) CD4(+) T cells, 213/mm(3) and 425/mm(3) naive CD4(+) T cells, and 10 200 and 5700 T-cell receptor rearrangement excision circles per 100 000 CD3(+) cells, respectively. They have normal CD4 T-cell receptor β variable repertoires. Both subjects developed antigen-specific proliferative responses and have discontinued immunoglobulin replacement. In summary, thymus transplantation led to T-cell reconstitution and function in these FOXN1 deficient infants.

Figure 1

T cells are oligoclonal in subject 1 before transplantation but are polyclonal after transplantation in both subjects by flow cytometry. TCR diversity for CD4 (A) and CD3 (B) T cells was assessed for subject 1 before transplantation. (C) The latest diversity assessment in subject 1 is shown; (D) the latest assessment in subject 2 is shown. Note that the y-axis in the CD4 in panel A differs from the y-axis in CD4 panels C-D. (A,C-D) The shaded area represents the normal range ± 3 SD based on data from 19 healthy adults.

Figure 2

CD4 RNA spectratyping shows oligoclonality in subject 1 before transplantation and polyclonality in both subjects after transplantation. Subject 1 at (A) day −127 and (B) day 873 after transplantation; subject 2 at (C) day 368 after transplantation. The D_KL score for subject 1 pretransplantation (A) is 1.38 compared with the D_KL score of 0.19 after transplantation (B). For subject 2, the posttransplantation D_KL was 0.08 (C). Lower D_KL scores reflect greater diversity in the TCR repertoire. The “X” indicates panels with insufficient RNA concentrations. These panels were not included in the calculation of the D_KL score. NC indicates negative control.

Figure 3

Biopsy evaluation of thymus allografts shows thymopoiesis. Subject 1 (A-B) and subject 2 (C-D). Cytokeratin reactivity (A,C) and CD3 reactivity (B,D). Scale bar, 50 μm. The microscope was an Olympus VANOX AHBS3. The magnification was 40× using a 40× numerical aperture objective lens (Olympus SPLAN 40×). The photomicrograph was taken at room temperature. Neither imaging media nor fluorochromes were used. The camera used was an Olympus DP70 digital imaging camera. Acquisition software was Olympus DP Controller. Subsequently, Adobe Photoshop 6.0 was used to compose this figure.

Figure 4

T-cell subtype populations and PHA responses before and after thymus transplantation. Subject 1 is shown in (A-C); and subject 2 is shown in (D-F). (A,D) T-cell phenotypes are shown; (B,E) naive T cells are shown; and (C,F) proliferative responses to PHA is shown. (A-B) The data points starting at 2.1 years were obtained by the referring hospital laboratory. (D-E) The first 3 data points and the data points starting at 1.4 years after transplantation were obtained by the referring hospital laboratory. The phenotypes of the naive CD4⁺ and CD8⁺ T cells are as described in Table 1. (C,F) The asterisks indicate the values obtained in the referring hospital laboratories. The mean (solid line) and ± 2 SD (dotted lines) for healthy adult data are shown (C) for the referring and transplant center laboratories. (F) The lower limits of the normal PHA response observed in the referring hospital laboratory is indicated by the single dotted line.