Analysis of risk factors for the development of posttransplant lymphoprolipherative disorder among 119 children who received primary intestinal transplants at a single center.

UNLABELLED: Posttransplant lymphoproliferative disorder (PTLD) is a well-known complication after pediatric transplantation. We analyzed all potential risk factors to assess patient and graft outcomes of 119 children who received intestinal transplantations. MATERIALS AND METHODS: Between August 1994 and March 2005, 119 patients underwent cadaveric intestinal transplantation. Their median age at transplant was 1.4 years (range: 0.6-17), median weight was 9.5 kg (range: 4.7-67), and 57% were boys. The median follow-up among 49 ongoing survivors was 41 months (range: 4-121). All PTLD cases were biopsy proven. In the past 5 years, treatment included antiviral therapy, immunosuppression withdrawal, and use of rituximab. RESULTS: The incidence of PTLD was 11.8% (14/119). No patient experienced graft failure secondary to PTLD, while two patients died from PTLD (14.2%). The PTLD group was divided into an early onset group (<4 months, 6 of 14; 42.8%) and a late onset group (>2 years, 8 of 14; 57.2%). No patient experienced PTLD between 4 months and 2 years after transplantation. The use of OKT3 was the only significant risk factor for the development of PTLD. No factor was specifically associated with the early versus late development of PTLD. CONCLUSIONS: The only factor associated with a significantly higher risk of PTLD was the use of OKT3 to treat a rejection episode. Finally, since the the introduction of anti-CD20 antibodies as part of the treatment protocol for PTLD, the risk of death due to PTLD appears to have become manageably low.

Adoptive transfer of experimental autoimmune thyroiditis (EAT) in guinea pigs: requirement for Ia-positive antigen-presenting cells for in vitro activation of effector T cells.

Lymph node T cells from guinea pigs sensitized in vivo with guinea pig thyroglobulin (GPTG) could transfer experimental autoimmune thyroiditis (EAT) to normal syngeneic recipients after in vitro culture with GPTG or GPTG-pulsed peritoneal exudate cells (PEC). Although EAT effector T cells have been shown previously to be Ia negative at the time of transfer, the addition of specific anti-Ia serum to the cultures inhibited effector cell activation. The inhibitory effect of anti-Ia on effector-T-cell activation was shown to be due to inhibition of the function of antigen-presenting PEC rather than to an effect on the sensitized T cell. Moreover, only Ia-positive PEC could present antigen in this system and Ia matching between the PEC and the T cell was required for effective T-cell activation. GPTG-pulsed Strain 2 (EAT susceptible) and Strain 13 (EAT resistant) PEC could both present antigen to T cells from 2 X 13 F1 guinea pigs although Strain 2 PEC were more effective, suggesting that defective antigen presentation by macrophages may at least partially explain the relative resistance to EAT of Strain 13 guinea pigs. These results indicate that interaction between Ia-positive PEC and sensitized T cells in vitro is necessary for the development of active effector T cells that can transfer EAT.

Effect of guinea pig thyroglobulin in incomplete Freund's adjuvant on experimental autoimmune thyroiditis induced by in vitro-activated lymph node cells.

Guinea pigs injected with guinea pig thyroglobulin (GPTG) in incomplete Freund's adjuvant (IFA) have been shown to be unresponsive to challenge with GPTG in complete Freund's adjuvant (CFA). However, effector cells which transfer experimental autoimmune thyroiditis (EAT) can be demonstrated in cultured lymph node cells (LNC) of unresponsive animals, indicating that GPTG in IFA does not suppress the initial sensitization of EAT effector cells. LNC from unresponsive animals were unable to suppress the in vitro activation of effector LNC or to suppress EAT when cotransferred with effector cells. When GPTG in IFA was given to animals which were used as recipients of effector cells, the production of EAT was markedly suppressed. These results suggest that GPTG in IFA can suppress EAT either by preventing effector cells from interacting with the thyroid or by interfering with the function of a cell in the normal recipient which may interact with effector cells to result in the lesions of EAT.

Adoptive transfer of experimental autoimmune thyroiditis (EAT) with in vitro activated lymph node cells from thyroglobulin-sensitized guinea pigs: characterization of the cell that transfers EAT.

Relatively low numbers of lymph node cells (LNC) from Strain 2 or Strain 13 guinea pigs sensitized with guinea pig thyroglobulin (GPTG) could transfer experimental autoimmune thyroiditis (EAT) to normal syngeneic recipients after in vitro culture with GPTG. The EAT induced in recipients of cultured LNC was similar in incidence and severity to EAT induced by active immunization with GPTG in complete Freund's adjuvant. The cells that were effective in transferring EAT were shown to be immunoglobulin-negative, nylon wool nonadherent, and Ia-negative. The effector cells were sensitive to irradiation after in vitro activation, indicating that cell proliferation in the recipient is required for development of EAT. Recipient animals often developed moderate to severe lesions of EAT yet none had detectable delayed hypersensitivity to GPTG and the majority also had no detectable anti-GPTG antibody.

Transfer RNA structure by carbon NMR: C2 of adenine, uracil and cytosine.

Fourier transform 13C NMR spectra of E. coli tRNA enriched on 13C in either position 2 of adenine (60 atom % 13C) or in position 2 of uracil (82%) and cytosine (63%) were taken at 25.16 MHz over the temperature range 10 degrees - 76 degrees. For C2 of adenine the peak as initially 5 ppm wide, but narrowed to 0.5 ppm as the molecule unfolded. C2 of uracil displayed behavior similar to that of adenine while the cytosine peak, initially relatively narrow at low temperature, sharpened less dramatically. Comparison of spectra at 26.16 MHz and 67.9 MHz showed that the peak widths for folded tRNA were determined largely by chemical shift non-equivalence. T2 T2 measurements suggested that intrinsic line widths of most cytosine C2 peaks were 4 Hz and 2-3 Hz for uracil. Adenine C2 with a directly bonded proton had resonances of about 40 Hz line width. T1 values were measured for C2 of adenine and the ribose carbons of tRNA. Consideration of dipolar relaxation and chemical shift anisotrophy led to a calculated rotational correlation time of 1.6 +/- 0.4 x 10(-8) sec for the adenines and 1.3 +/- 0.3 x 10(-8) sec for the ribose carbons.

Production of specific site probes of tRNA structure by enrichment with carbon 13 at particular locations.

Escherichia coli C6 rel met cys was cultured in a stringently defined minimal medium containing 13C-enriched metabolites in order to (1) achieve maximal 13C isotopic enrichment of tRNA; and (2) produce site specific but natural, non-perturbing NMR probes of tRNA structure and function. Growth conditions were manipulated to achieve optimal culture growth concomitant with maximal in vivo incorporation of various 13C-enriched nucleic acid precursors, including L-[methyl-13C] methionine, [2-(13)C] adenine, and [2-(13)C] uracil. Effective blockage of purine biosynthesis de novo was accomplished with the addition of the antimetabolite 6-mercaptopurine to the growth medium. Transfer RNAs specifically 13C-enriched in all methyl groups (57 atom %), C2 of adenine (60 atom %), and C2 of uracil (82 atom %) and C2 of cytosine (73 atom %) have been produced.