2014 Immunological Investigations, 2014; 43(2): 160–169 ! Informa Healthcare USA, Inc. ISSN: 0882-0139 print / 1532-4311 online DOI: 10.3109/08820139.2013.860161 Tucaresol down-modulation of MUC1- stimulated human mononuclear cells Stephen E. Wright, 1,2,3,4 Kathleen A. Rewers-Felkins, 1 Nazrul I. Chowdhury, 1 Jewel Ahmed, 1 Sanjay K. Srivastava, 3 and Pamela R. Lockwood-Cooke 5 1 Women’s Health Research Institute, Department of Internal Medicine, Texas Tech University Health Sciences Center, Amarillo, Texas, 79106, USA, 2 Department of Microbiology & Immunology, School of Medicine, Texas Tech University Health Sciences Center, Amarillo, Texas, 79106, USA, 3 Biomedical Sciences, School of Pharmacy, Texas Tech University Health Sciences Center, Amarillo, Texas, 79106, USA, 4 Harrington Cancer Center, Amarillo, Texas 79106, USA, and 5 Department of Mathematics, West Texas A&M University, Canyon, Texas, 79016, USA Interaction between antigen presenting cells and T lymphocytes, through receptors and co-stimulatory molecules present on the surface of these cells, is one of the key means to modulate the adaptive immune system. Tucaresol, a Schiff-base-forming chemical, can be used as a substitute for the physiological donor of carbonyl groups of antigen presenting cells, which can interact with the amine groups of T lymphocytes to modulate the adaptive immune system. This study was done to determine whether tucaresol can enhance killing of cancer cells in vitro as well as protect non-obese diabetic severe combined immunodeficient mice from tumor development by mucin 1 stimulated human mononuclear cells through the adaptive immune system. The expected hypothesis was not supported. Percent specific lysis of MCF-7 tumor cells by mucin 1 stimulated human mononuclear cells was reduced by tucaresol. Furthermore, tucaresol abolished the protective effect of mucin 1 stimulated human mononuclear cells against MCF-7 breast cancer cell growth in non-obese diabetic severe combined immunodeficient mice. This study implies that tucaresol may be of use as an immunosuppressive agent. Keywords Immunosuppression, T lymphocytes, tucaresol INTRODUCTION Activation of the adaptive immune system requires an interaction between antigen presenting cells (APC) and T lymphocytes. Molecules that substitute for APC–T-cell interaction could simplify T lymphocyte activation. One such molecule is tucaresol, which is a Schiff-base–forming chemical that substitutes for the physiological donor of carbonyl groups of APC that combine with amine groups on T-lymphocytes (Rhodes, 1996). Tucaresol (589C80;4[2-formyl- 3-hydroxy-phenoxymethyl] benzoic acid), a substituted benzaldehyde, was Correspondence: Stephen E. Wright, Department of Internal Medicine, Texas Tech University Health Sciences Center, 1400 Wallace Blvd., Amarillo, Texas, 79106, USA. E-mail: stephen.wright@ttuhsc.edu