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INFLUENCE OF SOLAR RADIATION ON IMMUNITY, I [Vol. XXI, Part III,
Repetition of vaccine injections is insisted upon every 2 years for the maintenance
of effective protection in tropical lands, but in middle temperate regions vaccine
protection is supposed to last five to seven years. This fact is also borne out by
the results of immunization against rinderpest with goat tissue vaccine in the plains
and hill regions of India. Evidence is available to show that the duration of
immunity conferred by a single dose of goat tissue vaccine is longer in the cattle
of Mukteswar, which has a temperate climate due to its high altitude (7,500 feet
above sea level), than in the cattle of Izatnagar, which has a tropical climate.
Perhaps this can be attributed to the difference in the environmental temperatures
prevailing in these two places. More recently, Neitz and Riemerschmid [1944]
carried out experiments at Onderstepoort which clearly indicate the detrimental
influence of solar radiation on the course of ' Blue tongue' in sheep. The sheep
exposed to the sun showed distinctly severer reactions than those kept in the shade.
Strongest and most fatal reactions were observed during summer months when the
sheep were exposed to the sun and got sufficiently photosensitized, but exposure
during winter months has practically no influence on the course of the disease. The
authors considered probable that the above findings, which were in respect of a
certain infectious virus disease, viz. ' blue-tongue' in sheep, might also be true in
respect of other diseases.
From the foregoing, it is evident that no effort was made by any worker to
study the influence of solar radiation on the activity of the antibody-forming mecha-
nism as estimated by serum reactions, and it is with this end in view that the
present work is concerned. Two antigens were selected for the experiment.
One of them was Staphylococcus toxoid for immunizing rabbits. The end-point
in the Staphylococcus toxin-antitoxin titration using rabbit erythocytes as indicator
being very sharp and definite, this method was employed for estimating the speci-
fic antibodies of the immune sera. The other antigen selected was goat tissue
vaccine for immunization against rinderpest. Specific antibodies of the rinderpest
immune sera were estimated by the standard method which has been evolved and
adopted at the Indian Veterinary Research Institute. The object of selecting
rinderpest is that it is the most common and widespread cattle disease in India.
Goat tissue vaccine, which is being extensively used all over India as an immuniz-
ing agent, is known to produce mild reactions in the indigenous breeds of cattle
which are more resistant to the disease than the imported breeds and the hill cattle
in India. The results of the immunization are usually satisfactory under controlled
conditions, i.e., when the animals are tied up in the stalls after vaccination and kept
under observation during the period of immunization, but unfavourable reports
are very often received from the field indicating severe reactions in some of the
immunized cattle and sometimes early breakdown of the immunity conferred.
These unfavourable results are usually attributed to the faulty technique adopted
by the operator in the field or to the deterioration of the vaccine during its transit
from the place of manufacture to the field. But the most striking difference between
the stall and field conditions being the absence or presence of direct solar radiation,
one should think it probable that this environmental factor may be responsible
for the difference of results of immunization in cattle kept in these two situations.
Staphylococcus toxiod was selected as an immunizing agent in rabbits. Specific
antitoxin developed in the immune sera was estimated and the difference between