HLA-DR frequencies in very high col(V) reactive (TV-DTH net foot pad swelling > 25 x 10-4 inches) lung transplant recipients (A, black bars) or their donors (B, black bars) were compared to the HLA-DR frequency of controls (1200 subjects, open bars) and non-col(V) reactive or col(V)low (≤ 25 x 10-4 inches) lung transplant recipients (A, grey bars) or their donors (B, grey bars). HLA-DR frequencies of very high col(V) reactive recipients (and their donors) who later developed BOS 2 or 3 (hatched bars) were also compared to HLA-DR frequency of controls. There were no significant differences in the frequencies of any HLA-DR alleles between normal control subjects from the University of Wisconsin (n=1200) and lung transplant recipients/donors (n= 281 recipients) or patients screened using the TV-DTH assay (n=54), data not shown. The frequency of HLA-DR1 (33%) and –DR17 (46%) was significantly higher in transplant recipients with very high col(V) responses (>25 x10-4 inches, A) than in normal controls (16% and 22%, respectively). HLA-DR13 was significantly less represented in col(V) responsive recipients compared to normal controls (4% vs 23% in controls). The frequency of HLA-DR15 was significantly higher in the donors of subjects who developed a high response to col(V) (50%) as well as in the donors of subjects with BOS 2/3 incidence (63%) compared to the frequency in the normal controls (26%). The frequency of HLA-DR17 was significantly higher in the donors of patients that did not have very high col(V) responses. *=p< 0.05, **= p<0.01.