Use of flow cytometry to identify monoclonal antibodies that recognize conserved epitopes on orthologous leukocyte differentiation antigens in goats, lamas, and rabbits William C. Davis a, * , Karel Drbal b , Abdel-El-Aziz A.E. Mosaad c , Abdel-Rahman M. Elbagory c , Ahmed Tibary a , George M. Barrington a , Yong Ho Park d , Mary Jo Hamilton a a Washington State University, College of Veterinary Medicine, Pullman, WA, USA b Institute of Molecular Genetics AS CR, Videnska, Czech Republic c Minufiya University, Faculty of Veterinary Medicine, Sadat City, Egypt d Seoul National University, College of Veterinary Medicine, Seoul, South Korea Abstract Flow cytometry was used to screen a panel of 320 mAbs, submitted to the Animal Homologues Section of the HLDA8, for mAbs that recognize epitopes conserved on orthologous leukocyte differentiation antigens (LDA) in goats, lamas, and rabbits. Nineteen mAbs specific for CD11a (1), CD14 (3), CD18 (1), CD21 (1), CD29 (2), CD44 (2), CD47 (3), CD49d (1), CD172a (1), CD45RB (1), CD61 (1), RACT48A, and GBSP71A reacted with goat LDA. Twenty three mAbs specific for CD7 (1), CD9 (2), CD11a (1), CD14 (3), CD18 (4), CD29 (1), CD32 (1), CD44 (1), CD47 (4), CD49d (2), CD50 (1), CD80 (1), CD172a (1), and GBSP71A reacted with llama LDA. Eighteen mAbs specific for CD9 (2), CD11a (1), CD14 (2), CD18 (4), CD21 (1), CD44 (2), CD45RB (1), CD49d (1), CD209 (1), RACT48A, and GBSP71A reacted with rabbit LDA. The specificities of two cross reactive mAbs that recognize different conserved epitopes on all leukocytes in two species (RACT48A) and all three species (GBSP71A) have not been determined. The patterns of reactivity of most of the mAbs were consistent with patterns of reactivity noted on human leukocytes. The specificity of some cross reactive mAbs generated in non-human species were validated on human leukocytes. Further studies are needed to verify that CD7, CD32, CD45RB, CD50, and CD209 recognize orthologous molecules in the indicated species. # 2007 Elsevier B.V. All rights reserved. Keywords: Monoclonal antibody; Leukocyte differentiation antigens; Goat; Rabbit; Llama 1. Introduction Previous studies have shown that two parameter flow cytometry can be used to cluster monoclonal antibodies (mAb) that recognize the same or different epitopes on the same leukocyte differentiation antigens (LDA), based on the pattern of expression of the molecule on one or more lineages of leukocytes (Davis et al., 1987, 1995; Lanier et al., 1983). Comparative studies have shown this method can also be used to identify and tentatively cluster mAbs that recognize epitopes on orthologous LDA because the pattern of expression of many orthologous LDA has been conserved cross species. This observation has proven www.elsevier.com/locate/vetimm Veterinary Immunology and Immunopathology 119 (2007) 123–130 * Corresponding author at: Dept. Vet. Micro/Path., College of Veterinary Medicine, Washington State University, Pullman, WA 99164-7040, USA. Tel.: +1 509 335 6051; fax: +1 509 335 8328. E-mail address: davisw@vetmed.wsu.edu (W.C. Davis). 0165-2427/$ – see front matter # 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.vetimm.2007.06.024