Conversely, Butyrophilin-like 2 (BTNL2), which also resides in the class II MHC region on chromosome 6 and probably functions as a T-cell co-stimulatory molecule, has been shown to have a more modest association with sarcoidosis in black compared to white populations; this may be due to greater allelic diversity or an antagonistic effect of HLA class II risk alleles on BTNL2-associated risk in black samples (16). This evidence concerns the gene BTNL2 and sarcoidosis.