1. ¹ Department of Microbiology, Mie University School of Medicine, Tsu, Mie-ken, Japan
2. ² Institute of Laboratory Animals, Mie University School of Medicine, Tsu, Mie-ken, Japan

Correspondence: Dr H Tsumura, Department of Microbiology, Mie University School of Medicine, 2-174, Edobashi, Tsu, Mie-ken 514, Japan. Email: <tsumura@doc.medic.mie-u.ac.jp>

Received 16 June 1998; Accepted 28 September 1998.

Abstract

Nineteen mAb directed against murine fusion regulatory protein-1 (mFRP-1)/4F2/CD98 were isolated and their biological properties were analysed. Intriguingly, mFRP-1 was found to be an alloantigen, namely, FRP-1.1 (DBA/2 and CBA mice type) and FRP-1.2 (BALB/c, C57BL/6 and C3H/He mice type). The nucleotide sequences of FRP-1.1 and FRP-1.2 were determined, demonstrating that amino acid change at 129 (PR) is related to the alloantigenicity. mFRP-1 is expressed on thymocytes, on spleen cells, on peripheral lymphocytes and on blood monocytes, suggesting that the physiological role in vivo of murine FRP-1 is different from that of human FRP-1. The biological activities of antimFRP-1 mAbs showed by the present study are: (i) enhancement of Newcastle disease virus-induced cell fusion; (ii) suppression of HIVgp160-mediated cell fusion; and (iii) induction of aggregation and multinucleated giant cells of monocytes/macrophages.