Cell-mediated immunity and expression of MHC class I and class II molecules in dogs naturally infected by canine transmissible venereal tumor: Is there complete spontaneous regression outside the experimental CTVT?

Canine transmissible venereal tumor with spontaneous remission: case study with emphasis on clinical and cytopathological exams to monitor tumor evolution

“…Its transmission occurs through transplantation of viable tumor cells, mainly during mating (1,2,3) . This cell transplantation occurs as an allograft, and somatic tumor cells initially activate mechanisms to evade recognition barriers by the major histocompatibility complex (MHC) of the new host (4,5) . Tumor growth, as well as its biological behavior, depends on factors such as the number of viable cells transplanted, evasion of the immune system, target tissue permissive to transplantation, and the immune status of the affected animal (6) .…”

“…The rapid growth of lesions is related to mechanisms of evasion of immunological recognition through regulation of expression of MHC class I and II molecules, reducing the action of dendritic cells and Tcytotoxic response. This phase tends to last between three to six months in adult and immunocompetent dogs (2,3,5,8,9) . TVCT tends to be more aggressive in older dogs, puppies, and immunosuppressed dogs, with progressive or disseminated disease.…”

“…Outcomes are commonly characterized by hypercellular samples composed of round cells with round to oval nuclei, aggregated chromatin, and vacuolated cytoplasm, which ranges from scanty to abundant (12,16,17,18,19) . Although the phases of the disease are well characterized clinically and histologically in animals with experimentally induced CTVT, cases of spontaneous regression of CTVT are uncommon in dogs with naturally occurring neoplasia (2,5) . Studies evaluating the evolution phases of CTVT through cytopathological examination and its applicability in clinical routine are still scarce.…”

Tumor venéreo transmissível canino com remissão espontânea: estudo de caso com ênfase aos exames clínico e citopatológico para monitoramento da evolução tumoral

“…A transmissão se dá a partir do transplante de células tumorais viáveis, principalmente durante o acasalamento (1,2,3) . Esse transplante celular ocorre como um aloenxerto e as células somáticas tumorais inicialmente ativam mecanismos de evasão de barreiras de reconhecimento pelo complexo principal de histocompatibilidade (MHC) do novo hospedeiro (4,5) . O desenvolvimento tumoral, bem como seu comportamento biológico, dependem de fatores como número de células viáveis transplantadas, evasão do sistema imune, tecido receptor permissivo à transplantação e estado imunológico do animal acometido (6) .…”

“…O rápido crescimento das lesões está relacionado aos mecanismos de evasão ao reconhecimento imunológico, através da regulação da expressão de moléculas MHC classes I e II, reduzindo a ação de células dendríticas e da resposta Tcitotóxica. Essa fase tende a durar entre três e seis meses em cães adultos e imunocompetentes (2,3,5,8,9) . Em cães idosos, filhotes e aqueles imunossuprimidos, o comportamento biológico do TVCT tende a ser mais agressivo, com a manifestação de quadros progressivos ou disseminados da doença, podendo ocorrer focos metastáticos regionais ou à distância, e não evoluir para as próximas fases observadas em cães com boa resposta imunológica (3,7,10,11) .…”