Areal and volumetric bone mineral density changes after renal transplantation in children: a longitudinal study.

INTRODUCTION: The effect of renal transplantation on areal bone mineral density (aBMD) in children has previously been studied. However, most previous reports did not include estimation of volumetric bone mineral density (vBMD) or analyze longitudinal data in these patients. In addition, updated reference standards for aBMD in children have recently been made available. METHODS: This retrospective study describes the longitudinal effect of renal transplantation on aBMD and vBMD in a cohort of 40 pediatric kidney transplant recipients. Lumbar spine aBMD measurements were obtained using dual-energy X-ray absorptiometry prior to transplant and yearly thereafter. vBMD values and z-scores were estimated as described in the most recently published references. RESULTS: A significant decrease in average aBMD and vBMD z-scores was observed within 1 year posttransplant, which did not recover during follow-up. The negative effect of transplantation on vBMD was blunted and vBMD z-scores were higher compared to aBMD. Linear mixed-effects model analysis demonstrated that lumbar spine aBMD and vBMD z-scores were inversely related to yearly prednisone dose (g/m2) but this effect was diminished as glomerular filtration rate was increased. CONCLUSIONS: Bone mineral density was negatively affected by renal transplantation in this cohort of pediatric patients. Estimation of vBMD appears to be appropriate for interpretation of the BMD changes occurring after renal transplant in children. The inverse relation between BMD z-scores and yearly prednisone dose suggests that ongoing posttransplant corticosteroid therapy may be responsible for the negative effect of transplantation on bone mineral density in this cohort.

Kidney graft loss in children: implications for program development.

BACKGROUND: Graft survival in children who undergo kidney transplantation is lower than that in adults. The objective of the study was to review the experience of the first 22 years of operation of the regional pediatric kidney transplantation unit for Atlantic Canada, based at the IWK-Grace Health Centre, Halifax, and to use the results to improve graft survival. METHODS: All cases of kidney transplantation performed at the centre from 1971 to 1992 were reviewed and the data compiled with the use of a predetermined database outline. Data for first transplants were analysed and compared with those in North American databases. Of the 40 graft failures, 19 (48%) occurred within the first 3 months after transplantation, a rate similar to that at other centres. The overall survival rates tended to be slightly lower than those of international databases. The introduction of cyclosporine A as an immunosuppressant, in 1985, did not provide the expected marked improvement in survival. Infection frequently accompanied acute rejection, and there was a delay in treatment of infections and rejection after discharge home. On the basis of these preliminary findings, several program changes were made: 1) a sequential immunosuppression protocol was implemented, 2) the intensity of the medical surveillance was increased for the first 3 months after transplantation, with aggressive treatment of infections and rejections, 3) a dedicated pediatric transplantation team was established as a subset of the adult team and 4) pediatric-specific selection criteria for cadaver donors were formulated. After these changes were implemented, data were collected and analysed up to June 30, 1997. RESULTS: Graft survival rates at 1, 2 and 5 years improved dramatically. After the beginning of 1993, there were only 2 graft losses among 22 transplants. Only one of these occurred in the first 3 months, and it was due to recurrent disease. Twenty-four rejection episodes occurred (10 in the first 3 months after transplantation), but all were reversed easily with high-dose steroid therapy. INTERPRETATION: Sequential immunosuppression with close medical surveillance and early aggressive treatment of infection and rejection contribute to a marked improvement in kidney graft survival in children.

Regional accumulation of Pgp-1+ memory cells in senescent mucosal immune system.

The proportion of memory cells expressing the Pgp-1 surface marker, and subsets of T cells expressing L3T4 (CD4+ helper cells), Lyt-2 (CD8+ suppressor/cytotoxic cells), LFA-1 (lymphocyte function-associated antigen-1), and interleukin-2 receptors (IL-2R) on the cell surface in the spleen, regional lymph nodes (PLN), mesenteric LN (MLN), bronchial or mediastinal LN (BLN), Peyer's patches (PP), thymus, and bone marrow (BM) was studied in C57BL/6J mice of varying ages. Monoclonal antibodies (Mabs) IM7.8.1, FD4, GK1.5, 3.155, and FD441.8 were used to measure Pgp-1, IL-2R, L3T4 Lyt-2, and LFA-1 expressions, respectively. Optimal dose and kinetic studies were determined. The percentages of positive cells were determined by monoclonal antibody staining and flow cytometry or immunofluorescence microscopy. Using flow cytometric analysis, we found significant age-associated increases in the percentages of Pgp-1+ cells in the MLN as compared with a slight, but not significant, increase in the spleen. There were significant age-related increases in the percentages of Lyt-2+ cells in the spleen with no change in the MLN. The percentages of cells with the other phenotypic markers, L3T4, LFA-1, and IL-2R did not change with age in the spleen or MLN. Using immunofluorescence microscopy, the percentages of Thy-1.2+, Lyt-1+, and Lyt-2+ cells in different anatomical immune tissues did not change with age, except in the BLN and PP where there were significant age-related declines of the percentages of Thy-1.2+ and Lyt-2+ cells in the BLN, and of Lyt-1+ cells in the PP. These results indicate elevated levels of Pgp-1+ memory senescent cells in the MLN and these age-related shifts or changes in T lymphocyte subsets with age could contribute to the conserved immune responsiveness of senescent mucosal T lymphocytes.

Analysis of serum antibody repertoires by isoelectric focusing and capillary blotting onto nitrocellulose paper.

A rapid method for the analysis of antigen-specific human serum antibodies is described. After isoelectric focusing on thin agarose gels, serum proteins are transferred to nitrocellulose paper by capillary blotting. The kinetics of transfer indicated that ca. 90% of 125I-labelled isolated human immunoglobulins (IgG, IgA and IgM) are transferred to the nitrocellulose paper within 10 min. Probing of the nitrocellulose blot with 125I-labelled tetanus toxoid antigen followed by autoradiography reveals the total serum anti-tetanus toxoid antibody repertoire, including high molecular weight IgM. This procedure is rapid (results can be obtained in less than 12 h), sensitive and should prove very useful for detailed studies and analysis of antibody repertoires in body fluids and extracts

Age-related strain differences in the development of auto-anti-idiotypic antibody regulation in the splenic and mucosal-associated lymphoid systems.

In the present study, we examined the changes that occur with age in anti-idiotype-blocked, hapten-augmentable PFC in the mucosal-associated lymph nodes (MLN and BLN) and spleen of various strains of mice. 2-month-old 129/J, AKR/J, and C57L/J mice had a high percentage of hapten-augmentable PFC in their spleen, MLN, and BLN; however, by 6-11 months these values had declined considerably in the spleen, while mucosal values remained high. In contrast, 2-month-old C57BL/6J, DBA/2J, and C3H/HeJ mice had a low percentage of hapten-augmentable PFC in their spleen, MLN, and BLN; but by 6-11 months these values had increased considerably in the spleen, while mucosal values remained low. CBA/J and SJL/J mice maintained high and low levels, respectively, of hapten-augmentable PFC in their spleens, MLN, and BLN over the age span. NZB/BinJ mice were found to be low producers in the spleen, but high in the MLN and BLN at 2 and 6 months of age. These data indicate that there are strain differences in the development of auto-anti-idiotypic antibody regulation with age.

Natural killer (NK) cell activity in murine muscular dystrophy. II. Age-related tissue distribution and enhanced NK activity in the thymus of dystrophic mice.

The age-related tissue distribution of natural killer (NK) cell activity in murine muscular dystrophy was investigated. Lymphoid tissues including the spleen, thymus, mediastinal (or bronchial) lymph nodes (BLN), mesenteric lymph nodes (MLN), inguinal/popliteal lymph nodes (PLN1), and axillary/brachial lymph nodes (PLN2) were obtained from various aged normal (+/+) and dystrophic (dy2J/dy2J) C57BL/6J mice. Cell suspensions were incubated with 51Cr-labeled YAC-1 lymphoma target cells in a 4-hr 51Cr-release assay. The data indicated that dystrophic mice, at all ages studied, had elevated levels of NK activity in the spleen, BLN, MLN, PLN1, and PLN2 as compared with the normal age- and sex-matched control group. The NK activity in the thymocyte population from dystrophic mice at 2 weeks of age was found to be negligible, while at 8 weeks of age it was two-fold higher than that for the normal control group. In addition, dystrophic mice had an age-related decline in NK activity in all tissues after 10 weeks of age but the activity was still elevated at 40 weeks of age as compared with the normal control group. Target cell binding studies revealed that the number of conjugate-forming cells in thymocytes from 8-week-old dystrophic mice were found to be significantly higher than that found in normal mouse thymocytes using NK-sensitive YAC-1 tumor target cells. The number of cells bound per YAC-1 target cell ranged from 1 to 3 for dystrophic mouse thymocytes as compared with 1 to 2 for the normal control group. Thus, the data indicate an elevated NK activity in all lymphoid tissues studied from dystrophic mice of different ages. In addition, the thymus from dystrophic mice at 8 weeks of age contains an enhanced number of conjugate-forming NK cells and NK activity.

Aging and the mucosal-associated lymphoid system.

Several lines of evidence support the notion that the mucosal-associated lymphoid system differs from the systemic. It is possible that the mucosal lymphoid system may also differ from the systemic system with regard to immune competence with age. Our findings in these studies indicate a lack of age-associated immune dysfunction in the mucosal-associated lymph nodes: that is, mesenteric and mediastinal lymph node PFC responses of old mice that revealed no decline in magnitude were found to be highly heterogeneous with regard to antibody affinity and revealed no appreciable anti-idiotype-blocked, hapten-augmentable plaque-forming cells. By contrast, the number of splenic and, as well, draining peripheral lymph node IgM, IgG, and IgA anti-TNP PFC responses to TNP-BGG was found to decrease with age with a preferential loss of high affinity plaque-forming cells. This decline in immune activity in the systemic tissues coincided with the increased appearance of anti-idiotype-blocked, hapten-augmentable plaque-forming cells. This differential effect of aging on immune responses in vivo of mucosal and systemic lymphoid tissues imply a site preference for an age-related decline in immune function, and a division of the immune system into regulatory compartments during the normal immune response to antigen in old mice. The present demonstration of a differential effect of aging on immune function in vivo raises an important issue with regard to age-related host defense mechanisms. For example, it would seem reasonable to predict that if immune function totally wanes with age, old individuals would be greatly susceptible to disease and infection. On the contrary, host defense mechanisms relevant to infection show minimal alterations in healthy aged individuals. Thus, we believe that mucosal immunity may play a very important role in host defenses in elderly individuals.