The lack of antigenicity of tuftsin: a naturally occurring phagocytosis stimulating tetrapeptide

Tuftsin (Thr-Lys-Pro-Arg) is a naturally occurring tetrapeptide that stimulates all known functions of the polymorphonuclear leukocyte and macrophage cell lines. Tuftsin is located in the FC region of IgG between the 289 and 292 amino acid sequence of the CH2 domain. We describe unsuccessful attempts to generate antituftsin antibodies. In separate experiments tuftsin was chemically conjugated to methylated bovine serum albumin (CH3BSA), BSA, keyhole limpet hemocyanin (KLH) and purified protein derivative (PPD). Tuftsin was also polymerized with glutaraldehyde. Animals used for immunization were rabbits, roosters, and dogs. All experiments failed to produce antituftsin antibody. Probable reasons for the lack of antigenicity include: I) Lack of "foreignness" of tuftsin in mammal species. II) The small size of the tetrapeptide. III) Tuftsin may be exerting an adjuvant effect when coupled to foreign antigens and is therefore not recognized by the host immune system.