SUMMARYInfants undergoing open heart surgery often have all or part of their thymus removed. The activity of the immune system has not been investigated thoroughly in these children, and only shortly after the operation. Therefore, it was decided to investigate the activity of the immune system in more detail in children several years after their operation. Peripheral blood samples from 19 children who had undergone open heart surgery during their first months of life was collected (study group) and from 19 ageand gender-matched children (control group). The activity of the immune system was evaluated by measuring the number of different cell types in peripheral blood, the phenotype of lymphocytes and the response of T cells following in vitro stimulation by mitogen, tetanus toxoid and measles antigen. The study group had significantly lower counts of total lymphocytes, which was reflected in a lower number of T cells but not B cells. Furthermore, the study group had significantly lower proportion of T cells (CD3 + ) and helper T cells (CD4 + ), but not cytotoxic T cells (CD8 + ). The level of neutrophils in peripheral blood was significantly higher in the study group. This may indicate enhanced innate immunity when the acquired immunity is defective. The results indicate a shift to extrathymic T cell maturation, which is less efficient for CD4 + helper cells than for CD8 + cytotoxic cells.

SummaryOur previous study showed that children who had been partially or completely thymectomized during heart surgery as infants had lower proportions and numbers of total lymphocytes and reduced proportions of T cells (CD3

Objective-To perform an exploratory analysis of the relative contribution of single MHC genes to the pathogenesis of systemic lupus erythematosus (SLE) in a homogenous white population. Methods-MHC class II alleles and C4 allotypes were determined in 64 SLE patients and in ethnically matched controls. HLA-DR and DQ typing was performed by polymerase chain reaction amplification with sequence specific primers. C4 allotypes were determined by agarose gel electrophoresis. Results-The frequency of C4A*Q0 was significantly higher in patients than in controls (46.9% v 25.3%, p=0.002). HLA-DRB1, DQA1, and DQB1 alleles in the whole group of SLE patients were not significantly diVerent from those of controls. On the other hand increase in DRB1*03 was observed in the group of patients with C4A*Q0, as compared with patients with other C4A allotypes (p=0.047). There was no significant correlation between severe and mild disease, as judged by the SLEDAI, and HLADR, DQ alleles and comparing the patients with C4A*Q0 with those with other C4A allotypes there was no significant diVerence regarding clinical manifestations. Conclusion-The results are consistent with the argument that C4A deficiency contributes independently to susceptibility and the pathogenesis of SLE. C4A*Q0 in SLE patients in Iceland shows weaker linkage disequilibrium with DR3 genes than reported in most other white populations and emphasises the role of ethnicity.

The expression of the integrin aE (CD103), may enhance the retention of regulatory T cells to peripheral inflammatory sites and possibly contribute to their suppressive potential. The aim of this study was to define the regulatory role of IL-2 and TGF-b1 on the CD103 expression and the optimal in vitro conditions for the induction/expansion of human CD4 + and CD8 + Tregs. Cord blood mononuclear cells (CBMC) were stimulated under various culture conditions, including anti-CD3, anti-CD28, IL-2 and TGF-b1. TGF-b1 and IL-2 were both required for optimal expression of CD103. In addition, TGF-b1 and IL-2 synergistically induced CD103 expression on CD8 + T cells, whereas, only additive induced expression was noted on CD4 + T cells. Surprisingly, CD103 expression was not dependent upon CD28 costimulation. IL-2 also played a central role in CD103 expression by CD25 hi Foxp3+ Tregs. IL-2, TGFb1 and anti-CD3 defined the optimal stimulatory conditions favouring the induction/expansion of both CD4 + and CD8 + human Tregs from naive CBMC. Thus, this study provides new insights into the regulatory role of IL-2 upon CD103 expression by human cord blood CD4 + and CD8 + T cells. Furthermore, it identifies the in vitro culture conditions driving the differentiation of the novel phenotype CD4 + and CD8 + CD103 + CD25 hi Foxp3+ Tregs from human CBMC.