Eight novel MICB alleles, including a null allele, identified in gastric MALT lymphoma patients.

MICA and MICB, as members of the major histocompatibility complex (MHC) class I-chain-related genes (MIC), encode stress-inducible glycoproteins that act as activating ligands for NKG2D and gammadelta T-cell receptor-bearing cells. We here describe the identification of eight novel MICB variants, including a null allele, which were identified in peripheral blood leukocytes of gastric MALT lymphoma patients. Only two of the novel alleles are characterized by point mutations, whereas the other variants display a recombination of known exonic MICB sequences that may be best explained by intragenic conversions. The novel MICB null allele is characterized by a Cytosin (C) deletion in a stretch of four Cs beginning from nucleotide 135 of exon 2 that leads to a premature stop codon (TGA) at codon 66.