Immunity — Vaccines

Kai Tiaki : the journal of the nurses of New Zealand, Volume XVI, Issue 1, 1 January 1923, Page 13

Immunity — Vaccines

Dr. Gladys Montgomery.

(By

By immunity is meant non-susceptibil-ity to a given disease or to a given microbe under natural conditions or under conditions experimentally produced. Immunity may be possessed by an animal naturally and is then usually called natural immunity or it may be acquired either by passing through an attack of the disease or by means of artificial inoculation. One finds individuals who, m spite of repeated exposures to infectious diseases such as scarlet fever, small-pox, etc., never contract the infection. They seem to have some protective substances m their blood and are naturally immune. The fowl is quite immune to tetanus and animals for the most part are immune to syphilis. According to the means by which it i? produced, acquired immunity is of two kinds to which the terms active and passive are [generally applied. Active immunity results after an attack of typhoid fever, measles, etc., and may be artificially produced by the injection of the appropriate vaccines. During the process of active immunity the patient produces his own anti-bodies m increasing amounts until sufficient neutralising substances are present m the serum to overcome the infection of the particular invading microbes. In passive immunity the anti-bodies have been produced by some other person or animal and are injected as the various anti-tonic sera to neutralise the toxins or poisons m the patient's serum. There are two main theories of immunity which are more or less reconciliable with one another. 1- Metchnikoff's Phagocytic Theory. Metchnikoff found that the phagocytes — the white blood corpuscles — have the power of taking up and destroying microbes, red blood corpuscles, cells and cell debris, m fact, as acting as scavengers. The scavenger leucocytes are irregular cells which are constantly changing

their shape and sending out pseudopodia or projections of protoplasm which surround the foreign body, be it microbe or debris, and engulf it. Thereafter, if the microbe is "prepared*' by opsonins, etc., and is not too resistant its destruction is brought about by the digestive action of the white blood corpusclesLeucocytes, especially the polymorphonuclear variety increase greatly m numbers during infections, for instance, during puerperal fever and suppurating appendicitis. Still, the mere fact of numbers is not sufficient for the ingestion and destruction of the microbes. Other substances as well need to be produced m the blood serum, and of these the three chief ones are opsonins, agglutins and bacteriolysins. All three may be present m varying amount or one or other may be absent. Also there are prccipitins and a few other substances of not quite so marked importance. Opsonins are substances which render the microbes more palatable to the white blood corpuscles. Opsonins are normally present m the blood, but may be increased by the injection of a vaccine — that is, a collection of dead or attenuated microbes. After the injection of the vaccine for a short period there is a "negative phase" lasting about seven days, during which the patient's resistance to that particular infection is lowered- Nurses inocluated with typhoid vaccine should not be allowed m a typhoid ward or allowed to be m the vicinity of typhoid patients during the "negative phase." There follows, however, a "positive phase" when the "opsonic index" is found to be raised. The "opsonic index" is the ratio of the number of microbes ingested by the phagocytes of any patients blood to the number so engulfed by the white blood corpuscles of the blood from a normal healthy individual. Thus, m counting 100 white blood corpuscles from a patient's blood we find

The parent cell being deprived of some combining arms hastens to make good the loss and over-produces receptors which are cast free m the blood stream. Thus is ensured a plentiful supply of free anti-toxin to neutralise any circulating toxin m the blood. In your capacity of nurses you will often be asked the value of vaccines and also you will need to decide on occasions whether or no you are yourself willing to undergo vaccination for protective purposes. Vaccines consist of definite, so many millions; of dead bacteria or bacteria m an attenuated condition. They stimulate the production of opsonins and thus increase enormously the capacity of white blood corpuscles for engulfing and destroying certain bacteria. After a successful course of vaccine treatment, say for typhoid fever, the bacilli of typhoid fever should not be able to gain a hold m the body but should be promptly eaten up by the white blood corpusclesThe story of the discovery of vaccines is an interesting one- In 1789 when Lady Mary Wortley Montagu returned to England from Constantinople she introduced the custom prevalent m the East of inoculating for small-pox from the diseased to the healthy. In Gloucestershire, Jenner was m the habit of practising this person to person vaccination, but noticed that the dairy or farm people who had had cow-pox did not take the inoculation, m other words, were immune or non-sus-ceptible. This led him to the idea of vaccination with cow-pox which then became the practice for preventing smallpox. It was some 80 years later that the rationale of the practice became evident through Pasteur's researches. Pasteur m the midst of his researches and laboratory work was ever trying to find some way of making the bacteria less harmful to the human species. The result was brought about almost by accident. In 1879 Pasteur had been working on chicken cholera and before going on his holidays left some cultures. When ho returned he found that these same cultures

were no longer harmful and that injections of them into fowls did not cause death. Length of time had lessened considerably their virulence. From this little experience he got his idea of attenuating or making non-violent bacteria and of then using them as vaccines to bring about immunity. Pasteur's next endeavour was to find a vaccine for anthrax — a disease which was causing a high mortality amongst sheep and cattle m France and elsewhere. By growing the cultures of anthrax at a high temperature and keeping them a certain time he was able to make a vaccine preventive to anthrax- The science of Pasteur was called m question by some unbelievers and m consequence a great experiment was undertaken, 60 sheep being placed at Pasteur's service. Twenty-five of these sheep were inoculated with anthrax vaccine and 25 were uninoeulated, but kept separate, and ten were kept as controls. A fortnight later a lethal dose of anthrax vious was injected into each of the 50 sheep. Excitement ran high as a huge crowd was interested ir the experiment. The day after the anthrax inoculation, Pasteur received a telegram stating that one of his inoculated sheep had a temperature and then his courage flagged. He spent a sleepless night walking about m great agitation. Next day he visited the farm and found 22 of the uninoeulated sheep dead — the remainder died the following night, The inoculated sheep survived- Pasteur's triumph was complete and the possibility of preventive inoculation announced to the world.

His next great success was with hydrophobia for which dread disease he made an effective vaccine. He was able to immunise dogs against hydrophobia. He hesitated to apply it to a human being, but his hand was forced when a little child was brought to him having been bitten by a mad dog. The vaccine again was entirely successful. The principles thus involved have been followed up and vaccines made for typhoid, cholera, plajgue, boils, etc. Typhoid bacilli are grown m bouillon or broth for 48 hours and then killed by heating for an hour at 53 deg. C- .59 Carbolic is added as a preventative. Usually two inoculations are given at intervals of seven days. After the injection of the vaccine there is a ' ' negative phase." Unless a person can be isolated and protected during an epidemic it would seem useless to inoculate because of the "negative phase." It is the custom for all probationer nurses to be inoculated with the vaccine of typhoid or para-typhoid A and B soon after joining the hospital staff. Also it is a wise procedure for anyone proceeding to the East or to an infected districtDuring the great European War typhoid fever was a comparatively negligible disease and this m spite of the grossly insanitary conditions often owing to the general inoculation with the vaccines of typhoid and para-typhoid A and B. Vaccines are also used as curative measures encouraging as they do the defensive forces of the body — chiefly for boils, acne, some skin diseases, etc.

500 microbes ingested, giving an average of 5, and m the normal individual's blood we get 1000 microbes, an average of 10. Then the "opsonic index" would be 5 divided by 10 or only .5. The "opsonic index" is used as a guide m vaccine treatment, especially m tuberculin, T.B. vaccine therapy. The richer the blood serum m opsonins the higher the "opsonic index- " The opsonic index usually rises after the stimulation of a vaccine. Agglutins appear m the blood m the course of most infections and have the property of "clumping" or agglutinating and rendering motionless mobile bacteria. This agglutinating quality is made use of for the purpose of diagnosis, for example, serum from a typhoid patient m about the second week of the disease will clump the typhoid bacilli m suitable dilutions. A "positive Widal" means that the patient's serum has agglutinating quality, m other words has arrived at the stage m which the anti-bodies, agglutinins, have beigun to appear m the serum. Similarly, serum from a patient with para-typhoid disease will agglutinate the bacilli of para-typhoid m certain dilutions and so on with other bacteria. Bacteriolysins are anti-bodies produced m response to an infection and have the power of shrivelling up microbes and causing them to become granules of debris. 2. The other theory of immunity is one propounded by Ehrlich. According to Ehrlich there exist m the body fluid cells which have arms or receptors of various kinds — one arm for combining with a food mass, one for combining with a toxin molecule. Toxins are the poisons produced by bacteria during their growth. When the toxins are manufactured by the bacteria they are shed into the blood stream where they settle, combining with the toxin receptors of the cells- As these combine they are shed off from the cell into the blood stream, forming a harmless body composed of toxin and anti-toxin joined as On the principle of the lock and key.