CANCER LETTERS ELSEVIER Cancer Letters 97 (1995) 117-122 Increase of a guinea pig natural killer cell (Kurloff cell) during leukemogenesis Claire Debout*, Sdid Taouji, Jacques Izard Laboratoire d’Histologie et de Biologic cellhire, UFR de Mtdecine, CHU C&e de Nacre, 14032 Caen Cede& France Received 2 August 1995; accepted24 August 1995 Abstract The guinea pig Kurloff cell (KC) is an estradiol-dependent circulating mononuclear cell that has natural killer cytotoxic activity in vitro. We studied the variation of KC number during the development of transplanted leukemia in inbred strain 2 (S2) leukemia-sensitive guinea pigs. Grafts of leukemic cells (L2C) produced a significant increase in the number of KC. Leukemia occurred in 35.5% of non-estrogenized animals and in 18.3% of estrogenized guinea pigs. The increased number of KC seems to have antileukemia activity in vivo. This could be part of the general phenomenon of cancer resistance in guinea pigs. KeywonLr: Kurloff cell; Natural killer activity; Leukemia; Guinea pig; Cancer resistance 1. Introduction Many studies from the 1950s to the 1970s showed the exceptional resistance of guinea pigs to spontane- ous tumors and carcinogen-induced or tumor homo- graft-induced cancers (for review see Ref. [5]). Nev- ertheless, some authors [4] who managed important guinea pig husbandries, reported the development of a spontaneous B-lymphoblastic leukemia in 5% of strain 2 (S2) inbred guinea pigs. From these leukemic animals, the leukemic L2C cells have subsequently been propagated by serial cell-graft transfers into leukemo-sensitive S2 guinea pigs. The success rate of the takes of L2C leukemic cells depends on the num- -- * Corresponding author. Fax: +33 31064508. ber of tumor cells transplanted and on the mode of transplantation (subcutaneous, intradermal or in- tracardial injections). On the other hand, a characteristic of the guinea pigs is a particular circulating lymphocyte named the Kurloff cell (KC) [7]. This estrogen-dependent KC is easily identified with a voluminous lysosomal inclu- sion, metachromatic and acid periodic Schiff posi- tive, full of proteoglycans [17] and hydrolasic en- zymes [27], as are the small intracytoplasmic gran- ules of natural killer (NK) cells (i.e. human or murine large granular Iymphocytes). The NK cytotoxic ac- tivity of the KC has been demonstrated in vitro in heterologous systems with the human target cell K562 [8], and murine target cells YAC-1 and WEHI 164 [21], and in a homologous system using the guinea pig target cell L2C [6]. 0304-3835/95/$09.50 0 1995 Elsevier Science Ireland Ltd. All rights reserved SSDI 0304-3835(95)03960-5