|MadSci Network: Immunology|
John, The immune cells of most species of animals are not well studied. The exception is the mouse, which has been extensively studied. Similar cell types, receptor molecules, and molecular signaling pathways exist in both humans and mice. It is likely that the immune systems of other mammals are similar to those of humans. Birds have a cellular immune system that is similar to mammals, with some notable differences. However, invertebrates lack antibody-producing cells or even lymphocytes, which confer specificity to immune reactions. Reponse to infection is conferred by cells and peptides that react to "abnormal" conditions. In general, one can say that the complexity and specificity of the immune systems of different animals is related to the complexity of the animal itself.
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