Abstract
Vascular endothelial cells were labelled with 10 vegetal lectins and 3 more monoclonal antibodies antiblood group ABO substances, in major organs of 14 common laboratory animals. After fixation in PLPa and paraffin embedding, cells were examined to determine their likeness to human cells. The most interesting reactive used was EEA, whose positivity defines upper mammalians. Blood B substance positivity and CSA negativity defines primates among which man is unique and defined by UEA I positivity and variability in ABO substance. CSA positivity defines non-primate upper mammalians. Rodents and birds were negative with all reactives tested. From the histochemical point of view, the animals closest to humans are monkeys, followed by swine and oxen, then by cat and dog and lastly by sheep. Rodents appear unrelated to humans in this system.