Submitted to: Veterinary Immunology and Immunopathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 12, 1997
Publication Date: N/A
Interpretive Summary: A panel of 196 monoclonal antibodies that react with cell surface antigens, termed clusters of differentiation (CD) antigens, were analyzed during the Second International Swine CD Workshop. From this panel a subset of 48 antibodies were tested for reactivity with certain common leukocyte cell CD markers, the CD44 and CD45 markers. No new anti-CD44 monoclonal antibodies were identified during the workshop. A group of 11 monoclonal antibodies were defined as reactive with CD45. The availability of cloned and expressed swine CD45 enabled this set of monoclonal antibodies to be further defined for reactivity with specific expressed isoforms of the CD45 molecule, termed CD45RA, CD45RC, CD45RO and CD45RAC. This manuscript describes the formal verification of the reactivities of these monoclonal antibodies and the comparison of their ability to bind to swine B and T cells. These well characterized monoclonal antibodies will help pig researchers to identify newly activated immune cells versus memory cells using the different CD45 monoclonal antibodies as specific markers. As disease and vaccine responses are characterized in pigs these will be useful reagents to show that pigs have been previously sensitized to an infectious agent.
Swine cell binding analyses of a set of 48 monoclonal antibodies (mAbs), including eleven standards, assigned to the CD44 and CD45 subset group of the Second International CD Workshop yielded 13 clusters. Although none of these corresponded to CD44, seven mAbs formed a cluster which was identified as being specific for restricted epitopes of CD45 (CD45R). The specificity of all the mAbs in the CD45R cluster was verified by their ability to immunoprecipitate distinct proteins and to react with CHO cells expressing individual isoforms of CD45. Three CD45R mAbs (3a56, MIL5,-a2) did react with a 210 kDa isoform(s), while another three (STH267, FG2F9, 6E3/7) only recognized a 226 kDa isoform(s). The remaining one (MAC326) precipitated both a 210 and 226 kDa protein. The specificity of all the mAbs in the CD45R cluster, and of the CD45 common mAbs, was confirmed by their reactivity with CHO cells transfected with cDNAs encoding the extracellular and transmembrane portions of distinct CD45R isoforms. Thus three mAbs (6E3/7, STH267, and FG2F9) appear to be specific for an epitope(s) encoded by the A exon, while one (MAC326) recognizes a determinant encoded by the C exon. The remaining three mAbs (3A56, -a2, MIL5) are apparently specific for an epitope(s) which results from the fusion of the C exon to the invariant leader sequence and is destroyed by inclusion of the A exon. When the natural expression of CD45RA isoforms was examined by reacting lymphocytes with CD45R mAbs, a high level expression CD45RA was detected in all B cells; the density of expression of the CD45RC ranged from undetectable to high in CD4+T cells. Overall this panel of CD45 mAbs will be very useful in analzying the maturation and differentiation of swine lymphoid cells subsets.