Immunologic Reactivity to Soluble Autochthonous Tumor Extracts in Dogs with Spontaneous Maligancies

Abstract

The presence of tumor-associated antigens (TAA) in dogs with spontaneous lymphoma (L) or solid tumors (ST) was investigated by testing soluble tumor cell extracts for their ability to stimulate autochthonous in vitro lymphocyte blastogenesis and in vivo intradermal delayed hypersensitivity responses. Tumor extracts were prepared from tumor biopsies and control extracts were prepared from buffy-coat cells of tumor dogs by hypertonic KCl solubilization. Blastogenic responses to intact, cryopreserved, autochthonous tumor cells were also determined.Fifteen of 26 (58%) L dogs and 23 of 32 (72%) ST dogs had positive blastogenic responses to at least one concentration of autochthonous tumor extracts. Blastogenic responses to tumor extract and to cryopreserved whole tumor cells correlated well when the tests were performed simultaneously. No consistent effect of autochthonous serum on the lymphocyte response to autochthonous tumor extract was observed.Two of 11 L dogs showed a positive skin test to autochthonous tumor extract and none reacted to control extract. Three of 21 ST dogs showed a positive skin test and two had a borderline response, while two ST dogs had a positive response to control extract. However, five of seven L and nine of 18 ST dogs were anergic as defined by failure to respond to intradermal PPD challenge after sensitization with Bacille Calmette-Guerin.In conclusion, lymphocytes from most dogs with spontaneous tumors underwent blastogenesis in vitro in response to autochthonous soluble tumor extracts, and these responses when tested simultaneously correlated well with responses to cryopreserved intact tumor cells. These results are compatible with the presence of TAA in extracts from cells of spontaneous canine tumors. Delayed skin test reactivity, however, was an uncommon and unpredictable finding, and does not appear to be useful in detecting TAA in the dog.