The present invention provides a polynucleotide which identifies and encodes a novel human macrophage antigen (TMAH). The invention provides for genetically engineered expression vectors and host cells comprising the nucleic acid sequence encoding TMAH. The invention also provides for the use of substantially purified TMAH and its agonists, antibodies, antagonists or inhibitors in pharmaceutical compositions for treatment of diseases associated with expression of TMAH. The invention also describes diagnostic assays which utilize the polynucleotide to hybridize with the genomic sequence or transcripts encoding TMAH and anti-TMAH antibodies which specifically bind to TMAH.