Cellular immunity: Observations on natural and acquired immunity to cobra venom

While the properties acquired by the serum of an animal as the result of immunisation to a toxin of the bacterial type have been examined with an exhaustive minuteness, little of the now vast literature on immunity has concerned itself with the cellular as opposed to the humoral aspect of immunity. Little, and less that is certain, is known of the changes that immunisation produces in living cells other than the white blood corpuscles. The part played by these cells in immunity processes, so fruitfully studied by Metchnikoff and others, is responsible by itself for an extensive literature which cannot be dealt with here. Accurate information is still wanting in regard to the part played by other living cells in the acquistion and retention of immunity. One reason for this is that investigation has been confined too exclusively to the blood. This has been partly and justifiably due to the diagnostic, therapeutic, and other importance of immune sera; also, perhaps, to the fact that the technique of blood investigation is more easy and generally familiar than the technique necessary to deal with other tissues. Another reason, no doubt, is that there are relatively few toxins which produce true immunity that lend themselves to the kind of investigation adopted in the experiments to be described. Without attempting the task, here unnecessary, of making a complete survey of the literature on cellular immunity, I wish to state briefly the present state of knowledge in regard to certain factors which have been investigated as explanatory of (a ) natural, and (b ) acquired immunity.