The body's immune system alone was not enough to prevent epidemics of these diseases, and treatment with antibiotics tipped the balance in our favour. If strains of these pathogens are selected due to improper use of antibiotics, there will be fewer medical alternatives. Never say that a bacterium is immune to, or has immunity to, an antibiotic, for instance. Resistance applies to the ability of a micro-organism to survive the effects of an antibiotic. Since resistance to antibiotics is likely to be genetically based, there is fear that populations of resistant strains may become established.
Passive immunity is based on ready-made antibodies.
Passive immunity may also be obtained via serum - derived from blood of organisms exposed to a pathogen. The specificity of this antigen-antibody reaction can be of even more use to Man when it is further refined and developed. Since several different lymphocytes are involved in the production of a cocktail of antibodies, these are known as polyclonal antibodies . A method of using the specificity of action of single antibodies in the lab was recently discovered by Cesar Milstein and co-workers, who made it possible to produce pure antibodies to almost any substance, to order. However they had to overcome a problem that lymphocytes only survive inside a living body - they cannot be grown in the laboratory in the same way that some other cells can.