Post-transplantation B cell function in different molecular types of SCID

Abstract

Purpose: Severe combined immunodeficiency (SCID) is a syndrome of diverse genetic cause characterized by profound deficiencies of T, B and sometimes NK cell function. Non-ablative HLA-identical or rigorously T cell-depleted haploidentical parental bone marrow transplantation (BMT) results in thymus-dependent genetically donor T cell development in the recipients, leading to a high rate of long-term survival. However, the development of B cell function has been more problematic. We report here results of analyses of B cell function in 125 SCID recipients prior to and long-term after non-ablative BMT, according to their molecular type.

Methods: Studies included blood immunoglobulin measurements; antibody titers to standard vaccines, blood group antigens and bacteriophage Φ X 174; flow cytometry to examine for markers of immaturity, memory, switched memory B cells and BAFF receptor expression; B cell chimerism; B cell spectratyping; and B cell proliferation.

Results: The results showed that B cell chimerism was not required for normal B cell function in IL7Rα-Def, ADA-Def and CD3-Def SCIDs. In X-linked-SCID, Jak3-Def SCID and those with V-D-J recombination defects, donor B cell chimerism was necessary for B cell function to develop.

Conclusion: The most important factor determining whether B cell function develops in SCID T cell chimeras is the underlying molecular defect. In some types, host B cells function normally. In those molecular types where host B cell function did not develop, donor B cell chimerism was necessary to achieve B cell function. 236 words.

Fig. 1

a) Serum concentrations of IgA , IgM X and IgE : prior to (a) and at the latest time studied after (b) rigorously T cell-depleted nonablative related donor bone marrow transplantation. The symbols represent individual patients, the bars the means and the vertical lines 2 SD above and below the means. Normal control values are for age 6 months in (a) and for older children and adults in (b).

Fig. 1

a) Serum concentrations of IgA , IgM X and IgE : prior to (a) and at the latest time studied after (b) rigorously T cell-depleted nonablative related donor bone marrow transplantation. The symbols represent individual patients, the bars the means and the vertical lines 2 SD above and below the means. Normal control values are for age 6 months in (a) and for older children and adults in (b).

Fig. 2

Antibody responses to bacteriophage Φ ×174 in all 61 SCID patients immunized with this vaccine post-transplantation. a) The mean peak antibody response to bacteriophage for CD3-Def SCIDs was significantly smaller (p<0.0001) than the mean peak antibody response to bacteriophage for the normal controls, but those for all other SCID types were not significantly different from those of normal controls [58]. b) The mean percentages of IgG antibody made after the second immunization were significantly lower than normal in Jak3Def (p<0.0001), X-Linked (p<0.0001) SCIDs and ADA-Def (p=0.0475) SCIDs. Those with Jak3Def SCID had an even lower mean percentage of IgG antibody those with X-linked SCID (p=0.0156). All other comparisons were not significantly different from normal controls [36]. All patients have donor T cells and good T cell function.

Fig. 2

Antibody responses to bacteriophage Φ ×174 in all 61 SCID patients immunized with this vaccine post-transplantation. a) The mean peak antibody response to bacteriophage for CD3-Def SCIDs was significantly smaller (p<0.0001) than the mean peak antibody response to bacteriophage for the normal controls, but those for all other SCID types were not significantly different from those of normal controls [58]. b) The mean percentages of IgG antibody made after the second immunization were significantly lower than normal in Jak3Def (p<0.0001), X-Linked (p<0.0001) SCIDs and ADA-Def (p=0.0475) SCIDs. Those with Jak3Def SCID had an even lower mean percentage of IgG antibody those with X-linked SCID (p=0.0156). All other comparisons were not significantly different from normal controls [36]. All patients have donor T cells and good T cell function.

Fig. 3

a) Prior to transplantation, the mean number of CD19+ B cells was significantly larger (p=0.0005) for the X-Linked SCIDs than that for the normal controls, while the mean number of CD19+ B cells was significantly smaller in ADA-Def SCIDs (p<0.0001) than that for normal 6 month old controls. B cells were not detected in RAG-Def, CHH and Artemis-Def SCIDs (not shown). X- linked, Jak3-Def and IL7Rα-Def SCIDs also had markedly increased expression of three molecules present on immature cells: CD10, CD5 and CD38 (Fig.3a) (p<0.0001, 0.0035, <0.0001). b) At the latest time studied post-transplantation, the mean number of CD10+ B cells for X-Linked SCIDs was significantly larger (p<0.0059) when compared to normal adult controls, but the mean numbers for all other SCID types were not different from normal.

Fig. 3

a) Prior to transplantation, the mean number of CD19+ B cells was significantly larger (p=0.0005) for the X-Linked SCIDs than that for the normal controls, while the mean number of CD19+ B cells was significantly smaller in ADA-Def SCIDs (p<0.0001) than that for normal 6 month old controls. B cells were not detected in RAG-Def, CHH and Artemis-Def SCIDs (not shown). X- linked, Jak3-Def and IL7Rα-Def SCIDs also had markedly increased expression of three molecules present on immature cells: CD10, CD5 and CD38 (Fig.3a) (p<0.0001, 0.0035, <0.0001). b) At the latest time studied post-transplantation, the mean number of CD10+ B cells for X-Linked SCIDs was significantly larger (p<0.0059) when compared to normal adult controls, but the mean numbers for all other SCID types were not different from normal.

Fig. 4

CD27+ (memory) B cells: a) Prior to transplantation the mean percentages of CD19+/CD27+ B cells for IL7Rα-Def, Jak3-Def, and X-Linked SCIDs were significantly smaller (p<0.0001, 0.020, <0.0001) than that for normal controls. b) Post-transplantation the mean percentages of CD19+/CD27+ B cells remained significantly smaller than normal only for the Jak3-Def and X-Linked SCIDs (p<0.0001, <0.0001). Patients shown included those who were or were not receiving IG therapy.

Fig. 4

CD27+ (memory) B cells: a) Prior to transplantation the mean percentages of CD19+/CD27+ B cells for IL7Rα-Def, Jak3-Def, and X-Linked SCIDs were significantly smaller (p<0.0001, 0.020, <0.0001) than that for normal controls. b) Post-transplantation the mean percentages of CD19+/CD27+ B cells remained significantly smaller than normal only for the Jak3-Def and X-Linked SCIDs (p<0.0001, <0.0001). Patients shown included those who were or were not receiving IG therapy.

Figure 5

B cell proliferative responses in vitro. Each point represents the proliferation index of cultures of B cells isolated from X-SCID patients [n=4 in (a), n=5 in (b),(c)], from IL7Rα-Def SCID [n=2 in (a),(b),(c)] patients and normal controls [n=8 in (a), n=9 in (b),(c)] stimulated with IL-21 + anti-CD40 (a), with IL-4 + anti CD40 (b), or with CpG (c) The horizontal bars represent the mean value of each series.