CD28/CTLA-4 ligands: the gene encoding CD86 (B70/B7.2) maps to the same region as CD80 (B7/B7.1) gene in human chromosome 3q13-q23.

CD86 (B70/B7.2) is an antigen of the immunoglobulin superfamily expressed on monocytes, dendritic cells and activated B, T, and natural killer cells. CD86 was recently identified as a second ligand for the T cell antigens CD28 and CTLA-4, and plays an important role in the co-stimulation of T cells in a primary immune response. We report here the assignment of the CD86 gene to human chromosome 3 using Southern blot analysis on a panel of hamster x human somatic cell hybrid genomic DNA. Fluorescence hybridization in situ on metaphase chromosomes coupled with GTG banding (G-bands by trypsin using Giemsa staining) confirmed this assignment and localized the CD86 gene to 3q13-q23 region. The CD86 gene is, therefore, located in the proximity of the CD80 (B7/B7.1) gene, the first identified ligand for CD28 and CTLA-4, previously mapped to chromosome 3q13.3-q21. Deletions, inversions and insertions of chromosome 3q21-q26, as well as translocations of 3q21 with other chromosomes have been described in many cases of acute myeloid leukemia (AML), acute non-lymphocytic leukemia (ANLL), chronic myeloid leukemia (CML) and myelodisplastic syndromes (MDS), suggesting that this region contains several genes involved in the leukemic process.