HLA and bird breeder's hypersensitivity pneumonitis.

HLA antigen status was assessed in non-related individuals and related family members with bird breeder's hypersensitivity pneumonitis (HP). 35% of 20 non-related patients carried HLABW40 compared to 10% of 861 normal controls (p less than 0.001, Pc less than 0.05, respectively). A consistent association of an HLA haplotype with disease was demonstrated in three of four families. Selected HLA antisera contained antibodies which blocked the blastogenic response to bird antigen. This study suggests the existence of an HLA associated Ir gene in bird breeder's HP.