Antibody response against neem leaf preparation recognizes carcinoembryonic antigen Koustav Sarkar a , Anamika Bose a , Subrata Laskar b , Soumitra K. Choudhuri c , Subhabrata Dey d , Purnendu K. Roychowdhury e , Rathindranath Baral a, ⁎ a Department of Immunoregulation and Immunodiagnostics, Chittaranjan National Cancer Institute, 37, S. P. Mukherjee Road, Kolkata-700026, India b Natural Product Laboratory, Department of Chemistry, Burdwan University, Burdwan, West Bengal c Department of Environmental Carcinogenesis and Toxicology, Chittaranjan National Cancer Institute, 37, S. P. Mukherjee Road, Kolkata-700026, India d Unit of HPLC, Chittaranjan National Cancer Institute, 37, S. P. Mukherjee Road, Kolkata-700026, India e ChemBiotech International, Salt Lake, Kolkata, India Received 1 September 2006; received in revised form 30 October 2006; accepted 31 October 2006 Abstract An immune serum generated in Swiss mice against an aqueous preparation from neem leaf was reactive with carcinoembryonic antigen (CEA) and a peptide sequence derived from it. Using ELISA, we have demonstrated that CEA reactive antibody titer (chiefly IgG2a) was significantly decreased after absorption of the immune sera with CEA. Neem leaf preparation (NLP) generated immune sera was also reactive with CEA in immunoblotting and CEA reactive component in the NLP sera can be immunoprecipitated. Identical recognition of CEA expressed on human colorectal cancer specimens, by anti-CEA monoclonal antibody and NLP sera was documented by immunohistochemistry. NLP generated sera could also react with NLP in ELISA and this reactivity was decreased after absorption of the NLP with anti-CEA antibody. Estimation of protein in NLP revealed the presence of it, at least 10% of the total dry weight. In addition, existence of flavone and quercetin was also evidenced from LC-MS analysis. Further studies are needed to identify the antigenic component may have some homology with CEA molecule. This unique property of neem may be utilized for the immunotherapy of CEA positive tumors. © 2006 Elsevier B.V. All rights reserved. Keywords: Antibody; Carcinoembryonic antigen; Neem leaf preparation 1. Introduction Neem (Azadirachta indica) is a widely prevalent and highly esteemed wonder tree of the Indian subcontinent and several of its beneficial properties are reported [1]. The environmental compatibility of neem products, the lack of resistance development to them, their harmless nature against non-target organisms and lack of toxicity- all have significantly enhanced the integrated use of neem in medicine [2]. We are working on a water soluble preparation of neem leaf (NLP), which was proved to be nontoxic, hematostimulatory and immu- nostimulatory [3]. This preparation has immunoprophy- lactic function to prevent the growth of murine Ehrlich's International Immunopharmacology 7 (2007) 306 – 312 www.elsevier.com/locate/intimp ⁎ Corresponding author. Tel.: +91 33 2476 5101/5102/ 5104x389x334; fax: +91 33 2475 7606. E-mail address: rbaral@hotmail.com (R. Baral). 1567-5769/$ - see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.intimp.2006.10.014