Macrophage and lymphocyte chimerism in bronchoalveolar lavage cells from human lung allograft recipients

Background. Chimerism. is suggested to predict a more favourable prognosis in solid organ transplantation. Material and method. Forty-eight bronchoalveolar lavages from 10 patients (5 females and 5 males) who had received sex-mismatched donor lungs were monitored for varying periods of time, of up to 2 years, at regular intervals (median 3.0 (0.5-24) months). To investigate the chimerism. in macrophages and lymphocytes in bronchoalveolar lavage cells a cloned 2.12 kilobase large biotinylated Y-chromosome-specific DNA-probe was used for in situ hybridization. Results. Donor macrophages disappeared in seven patients within the first 6 months after surgery (median 3.0 (1-6) months). But 15% donor macrophages could be detected in one patient 1 year and 10% in 2 patients two years after surgery. Donor lymphocytes disappeared in all patients within 3 months (median 1 (0.5-3) months). There was no correlation between periods or severity of acute rejection and percentage of donor macrophages and donor lymphocytes in bronchoalveolar lavage. None of the patients developed obliterative bronchiolitis. Conclusion. Macrophage chimerism. in lung may exist for several years. Whilst our results do not elucidate the role of local macrophage chimerism, they do not currently support the view that chimerism prevents rejection.