Expression of a 4‐(hydroxy‐3‐nitro‐phenyl) acetyl (NP) specific equi‐murine IgE antibody that mediates histamine release in vitro and a type I skin reaction in vivo

Abstract

Summary Due to characteristic clinical signs, immunoglobulins of isotype E (IgE) are believed to be involved in several allergic diseases of the horse. To date, closer investigations have been hampered by the fact that neither purified equine IgE nor anti‐equine IgE monoclonal antibodies were available for IgE isotype determination. As an approach to solve this problem, we constructed a stable cell line (EqE6) that expresses recombinant equi‐murine IgE specific for 4‐(hydroxy‐3‐nitro‐phenyl) acetyl (NP). Biochemical analysis of the purified protein revealed a highly glycosilated IgE monomer of approximately 230,000 Da. The biological ability of the NP‐IgE to mediate histamine release after crosslinking with antigen was demonstrated in vitro using equine blood leucocytes. In vivo, the intradermal application of NP‐IgE followed by antigen crosslinking induced a type I hypersensitivity skin reaction in horses. Both results indicate that the recombinant NP‐IgE contains an intact and functional FceRI binding site and mediates effector functions in equine basophils and cutaneous mast cells. This equi‐murine IgE can be used for the production of IgE‐specific polyclonal and monoclonal antibodies. In addition, the NP specificity allows the antigen‐specific activation of equine Fce‐receptor‐expressing cells, such as mast cells and basophils. This property could be used to investigate IgE‐mediated mechanisms for a better understanding of equine type I allergic diseases.

Tools to aid the diagnosis of equine allergy

“…In this issue (p 657), Wagner et al (2002) present a means to dissect IgE-mediated mechanisms in equine Type I allergic diseases, including the production of antibody reagents to equine IgE.…”