Pathogenesis Pathology I Flea infected with Y. pestis- hungry bites ferociously. The inoculated organisms may be phagocytosed by polymorphonuclear cells and macrophages, they produce the antiphagocytic protein and subsequently are able to resist phagocytosis The pathogens rapidly reach the lymphatics and an intense hemorrhagic inflammation develops in the enlarged lymph nodes which may undergo necrosis and become fluctuantPathogenesis & Pathology I • Flea infected with Y. pestis hungry bites ferociously. The inoculated organisms may be phagocytosed by polymorphonuclear cells and macrophages, they produce the antiphagocytic protein and subsequently are able to resist phagocytosis. • The pathogens rapidly reach the lymphatics and an intense hemorrhagic inflammation develops in the enlarged lymph nodes, which may undergo necrosis and become fluctuant