The limitations and advantages of studies in vitro It is frequently asserted that studies on immune effector mechanisms in vitro, however interesting in their own right, bear no relationship to the “real” situation in vivo. This is particularly true of parasitic diseases, for which the proponents of this point of view might use three arguments. The first is that, although a particular effector mechanism might be capable of mediating detectable damage to the parasite in vitro, the culture conditions under which the parasite is maintained are necessarily artificial and to a greater or lesser extent suboptimal. An organism which undergoes irreversible damage in vitro might be able to repair itself under more suitable conditions in vivo. Secondly, although a particular effector mechanism may be demonstrable in vitro, this mechanism may be blocked or inactivated by other processes that occur within the highly complex environment in vivo.
Present address: Department of Medicine, Harvard Medical School, Boston, Massachusetts 02120.