Desowitz, an immunologist with worldwide experience in parasitology, explains the human immune system with the same verve he demonstrated when writing about malaria and other pestilences in New Guinea Tapeworms and Jewish Grandmothers. The history is done in four sharp, short takes on Jenner, Pasteur, Metchnikoff, and Ehrlich. Desowitz is especially vivid in describing the trials and tribulations of Elie Metchnikoff, the moody Russian incarnate, who was given to bouts of depression and suicidal attempts. He survived to pursue the embryology of sea urchins and starfish, one night taking a thorn from a rose and inserting it into a starfish larva. The next morning he observed that the thorn had been engulfed by mobile amoeba-like cells that had rallied to the scene to feast on the foreign body. These ""phagocytes""--eating cells--remain a main line of cellular defense in all higher organisms. In contrast to Metchnikoff, Ehrlich looked not to cells, but to chemicals carried in the blood serum. These molecules--antibodies--were specific in attaching to, and disarming, bacterial toxins and even whole bacteria themselves. With such material as background, Desowitz describes how far we have come in dissecting the immune system at the cell and molecular level, going on, too, to discuss the importance of nutrition in immunity (he confesses which trace elements and vitamins he adds to his diet). Sadly, he recounts the world toll taken by infectious disease, especially among the malnourished. Of special note, he provides an up-to-date discussion of AIDS and of the difficulties in developing an AIDS vaccine. The potential for using genetic-engineering techniques and monoclonal antibodies against AIDS and other unconquered infections exists, however, and allows him to conclude this well-wrought, well-written work on an upbeat note.