Various Theories
Again, it is claimed that the phagocytes perform a very important function in protecting the body against invading microörganisms by attacking, destroying and digesting them. Another theory is that the antibodies of various kinds play an important part in keeping the body free from undesirable invaders. It is also asserted that immunity is produced in a negative way by the absence of a specific affinity between the tissue cells and the toxin.
Immunity may be the result, according to other theories, of a positive factor due to the presence of antibodies which neutralize the toxins. In some cases immunity is associated directly with cell activity while in others it is resident in the blood and fluids of the body. Rosenau further says, “The unsatisfactory state of our knowledge in certain fields of immunity is well illustrated in the case of anthrax. The mechanism of protection is not at all understood in this infection, which was the first and classic illustration of a germ dis-ease. The mechanism of immunity in common colds is also complex and obscure.”
Many other authors could be quoted to show that the real philosophy of immunity is not understood nor why a germ will seem to cause dis-ease in one individual and not in another. But this is sufficient to indicate the unsatisfactory results that have been obtained in research work along this line.