lmmunogenetics 26: 378-380, 1987 ]IlllllUno- genetics © Springer-Verlag 1987 A gene in the H-2S: H'2D interval of the major histocompatibility complex which is transcribed in B cells and macrophages Ikuya Tsuge 1, Fung-Win Shen 1, Michael Steinmetz z, and Edward A. Boyse 1 1 Memorial Sloan-Kettering Cancer Center, New York, NY 10021, USA 2 F. Hoffmann-La Roche & Co., Ltd., CH-4002 Basel, Switzerland In screening a mouse B-cell cDNA library for clones representing genes selectively expressed by B cells, we encountered a clone, B144, which appears to refer to a previously unrecognized gene between H-2S and H-2D. Some properties of this gene, which is not obviously clas- sifiable with other varieties of genes in the major histocompatibility complex (MHC), are described in this report. The B-cell cDNA library, containing .-~ 1.4 × 10 6 in- dependent transformants, was made using the pCD vector (Okayama and Berg 1983) and poly(A) + mRNA of 1.29 cells. 1.29 is a B-cell spontaneous ascites tumor that origi- nated in an I/St/Boy mouse. About 1 x 105 colonies of a sublibrary with insert sizes of 0.5-1.5 kb were screened with 32p-labeled 1.29 cDNA previously subtracted with mRNA of T-cell leukemias ISL57 and ASL1, sarcoma Meth A, and BALB/c liver. Positive clones were hybri- dized first with combined cDNA of B cells (NFS-1.3 and NFS-5) and then with combined cDNA of ISL57, ASL1, and Meth A. Colonies hybridizing preferentially with B-cell cDNA were selected. To eliminate clones representing known class II genes, colonies were further hybridized with a combination of 32p-labeled class II clones [pAAC6 (A~) (Benoist et al. 1983), A¢1/SP64-1 and A~2/Sp64-2 (Wake and Flavell 1985), cEBs2 (Ee) (Mengle-Gaw and McDevitt 1985) and 32.1 (E~) (3.4 kb Sal I fragment) (Steinmetz et al. 1982)]. This yielded 26 cDNA clones from which plasmid DNAs were isolated and used as probes in Northern blot- ting to assess selective expression by B cells. Three clones appeared specific for B cells but were found to represent an IgX2 gene and were not studied fur- ther. However, a further clone, B144, appeared to represent a novel or unidentified gene that is transcribed in B cells and macrophages. In Northern blotting with a nick-translated B144 probe, a single band of ~ 800 nucleotides was observed with total RNA of spleen and lymph node cells and of B and macrophage cell lines, but not ofT and other cell types named in Figure 1 nor of T leukemias ASL1, EL4, and K36 (not shown). In case a known class II gene had es- caped screening, Northern blots representing B144, A~, and E~ were compared. The B144 transcript appeared shorter than the 1.3 kb of usual class II transcripts and shorter than the reported lengths for CR3 complement receptor (Sastre et al. 1986) and FcT-receptor (Lewis et al. 1986) which also are selectively transcribed in B cells and/or macrophages. Fig. 2. Location of the B144 gene between H-2S and Qa-2 indicated Fig. 1. Northernblotsof total RNAhybridizedwith nick-translatedB144 by Southern blotting of liver DNA of H-2-recombinantcongenic mice