Inhalative challenges are important in the diagnosis of occupational asthma due to diisocyanates. As existing protocols are time-consuming and costly, it was the aim of this study to develop a short duration whole body exposure protocol. Ninety three subjects with suspected occupational diisocyanate-induced asthma and verified current or previous occupational exposure to diisocyanates and ten control subjects without diisocyanate exposure but with bronchial hyperresponsiveness were investigated. After baseline examination on the first day, subjects underwent a standardized whole body multiple-steps-1-day challenge with exposures of up to four times 30 min to concentrations of 5, 10, 20, and 30 ppb of the dominant diisocyanate used at work on the second day. Common spirometric and body plethysmographic parameters were used as positivity criteria. Overall, 14 subjects demonstrated a positive diisocyanate challenge, 19 were considered doubtful, and 60 were negative. All controls had negative challenges. Positive reactions occurred during the challenge (n = 10) or during follow-up (n = 4). Eight subjects showed >40 % fall of FEV1. These severe reactions occurred after 5 ppb (n = 2) or 10 ppb (n = 3), while isolated late reactions after 2 h of follow-up were not observed. Multivariate analysis showed an association between a positive challenge and both the degree of previous occupational exposure and the presence of baseline bronchial hyperresponsiveness. In summary, the proposed 4-steps-1-day diisocyanate challenge protocol induced pronounced bronchial reactions in a small number of subjects. As these reactions were more likely to occur after low concentrations, it is recommended to shift the initial concentration/dose step to lower exposures.

Intestinal IgA is strongly involved in microbiota homeostasis. Since microbiota disruption is a major risk factor of acute GvHD, we addressed the kinetics of intestinal IgA-positive (IgA+) plasma cells by immunohistology in a series of 430 intestinal biopsies obtained at a median of 1,5 months after allogeneic stem cell transplantation from 115 patients (pts) at our center. IgA+ plasma cells were located in the subepithelial lamina propria and suppressed in the presence of histological aGvHD (GvHD lerner stage 0: 131+/- 8 IgA+ plasma cells/mm2; stage 1-2: 108 +/-8 IgA+ plasma cells/ mm2; stage 3-4: 89+/-16 IgA+ plasma cells/ mm2, p 0.004). Overall, pts with IgA+ plasma cells below median had an increased treatment related mortality (p = 0.04). Time courses suggested a gradual recovery of IgA+ plasma cells after day 100 in the absence but not in the presence of GvHD. Vice versa IgA+ plasma cells above median early after SCT were predictive of relapse and relapse related mortality (RRM): Pts with low IgA+ cells had a 15% RRM at 2 and at 5 yrs, while pts with high IgA+ cells had a 31% RRM at 2 years and more than 46% at 5 years; multivariate analysis indicated high IgA+ plasma cells in biopsies (HR 2.7 (95% CI 1.04-7.00) as independent predictors of RRM, whereas Lerner stage and disease stage themselves did not affect RRM. In contrast, IgA serum levels at the time of biopsy were not predictive for RRM. In summary, our data indicate that IgA+ cells are highly sensitive indicators of alloreaction early after allo-SCT showing association with TRM but also allowing prediction of relapse independently from the presence of overt GvHD.

my family, and my friends for all of the guidance, support, patience, and time that they have given me throughout the thesis process. I am very grateful to have had the help and support of these people.

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