The mouse tag7 gene was cloned and characterized in our previous works. This work is devoted to identifying and cloning its homologs. The human homolog of the tag7 gene was cloned. Data of analysis of the primary structure of the human tag7 and results from the study of the production of the corresponding protein in human organs and tissues indicate that this gene plays a major role in the mammalian immune system. The mouse and human tagL gene carrying an extended region of structural homology with the tag7 gene was detected by computer analysis and was subsequently cloned. Sequence analysis suggested the possible membrane localization of the gene, whereas the specific expression pointed to the role of this gene in the immune system. Both genes, tag7 and tagL, were localized in the human chromosome 19.