Hypersensitivity to rabbit antithymocyte globulin in an islet transplant recipient: a case report.

OBJECTIVE: The aim was to describe a case of hypersensitivity to rabbit antithymocyte globulin (rATG) occurring in the context of islet transplantation. METHODS: A 36-year-old woman with type 1 diabetes was admitted for islet transplantation. rATG was administered the first day (1.5 mg/kg) with methylprednisolone (2 mg/kg), and on the second day (1.5 mg/kg) without glucocorticoid to avoid potential toxicity to the anticipated islet transplant. RESULTS: At the end of the rATG infusion on the second day she developed hives over her face, chest, and back and tender erythema at her intravenous site (Arthus reaction). Islet transplantation was not performed. She reported exposure to a pet rabbit for 2 years in childhood. Overnight, fever developed and the rash evolved into an erythematous morbilliform eruption affecting the torso. Serum high-sensitivity C-reactive protein (hsCRP) and the erythrocyte sedimentation rate (ESR) were elevated; serum complements C3 and C4 were normal. She received prednisone (50 mg) with subsequent resolution of the rash. Nine days after her initial reaction, she developed a recurrence of the rash and fever with arthralgias; levels of C3 and C4 had fallen. Methylprednisolone (125 mg, twice) was required for symptom improvement, and was gradually tapered as prednisone over the next 4 weeks with resolution of the complement, ESR, and hsCRP abnormalities. Five months after the initial attempt at islet transplantation, she returned to receive 7,879 IE/kg via portal vein infusion under basiliximab, etanercept, tacrolimus, and sirolimus immunosuppression and has required no to low-dose (0.1 U/kg/d) insulin to maintain near-normal glycemic control for > 12 months after transplantation. CONCLUSIONS: Our patient's initial hypersensitivity reaction to rATG was followed by immune-complex type 3 hypersensitivity (serum sickness) requiring high-dose glucocorticoids. Canceling the initial islet infusion proved to be wise, and the patient subsequently did well with islet transplantation under an alternative induction agent.

Secondary immunologic consequences in chromosome 22q11.2 deletion syndrome (DiGeorge syndrome/velocardiofacial syndrome).

Clinical evidence suggests that patients with Chromosome 22q11.2 deletion (Ch22q11.2D) have an increased prevalence of atopic and autoimmune disease and this has been without explanation. We hypothesized that the increase in atopy was due to homeostatic proliferation of T cells leading to a Th2 skew. We performed intracellular cytokine staining to define Th1/Th2 phenotypes in toddlers (early homeostatic proliferation) and adults (post homeostatic proliferation) with this syndrome. To attempt to understand the predisposition to autoimmunity we performed immunophenotyping analyses to define Th17 cells and B cell subsets. Adult Ch22q11.2D patients had a higher percentage of IL-4+CD4+ T cells than controls. Th17 cells were no different in patients and controls. In addition, adult Ch22q11.2D syndrome patients had significantly lower switched memory B cells, suggesting a dysregulated B cell compartment. These studies demonstrate that the decrement in T cell production has secondary consequences in the immune system, which could mold the patients' clinical picture.

A nonsense mutation in exon 3 results in the HLA-B null allele B*5127N.

A new HLA-B null allele has been identified within the B*51 group by combined serological and molecular typing of an Italian Caucasoid family. Serological data indicated that the proband typed homozygous for A2 and B60. Confirmatory typing using sequence specific oligonucleotide hybridization (SSPOH) detected a second B allele within the B*51 group. Allele specific typing (SSP) for B*51 subtypes, including the known B*5111N allele, was performed, and typing results were consistent with B*5101, suggesting the presence of a new null variant. Cloning and sequencing of this allele identified a B*5101 variant with a nonsense mutation in exon 3. This new null allele has been designated B*5127N. The combined use of serologic and DNA-based typing methods facilitates the identification of null and low-expression alleles. An overview of null alleles of class I HLA is presented.