Rl. Sepulveda et al., TUBERCULIN REACTIVITY AFTER NEWBORN BCG IMMUNIZATION IN MONOZYGOTIC AND DIZYGOTIC TWINS, Tubercle and lung disease, 75(2), 1994, pp. 138-143
Setting: Studies showing significantly higher concordance of tuberculo
sis among monozygotic twins than dizygotic twins have provided support
for genetically determined susceptibility to tuberculosis. Objective:
We wished to explore whether the development of delayed type hypersen
sitivity to tuberculin after newborn BCG immunization of twins suggest
ed genetic regulation of the response to BCG in humans. Design: Our st
udy population consisted of 17 monozygotic twin pairs, 18 dizygotic tw
in pairs, and 64 single infants 3-34 months of age from Santiago, Chil
e. All had a BCG scar and were tuberculin tested by one trained nurse.
Results: The mean birth weight of both groups of twins was significan
tly lower than that of singletons and the percentage of individuals wh
o failed to respond to tuberculin was approximately twice as high in t
wins as in singletons. After adjustment for birth weight and age by re
gression analysis, it was found that the distribution of tuberculin re
activity in both monozygotic and dizygotic twins was not significantly
different from that of singletons. Both twin pair correlations in adj
usted tuberculin reactivity were significantly greater than zero (P <
0.01) and led to a heritability estimate of 0.28. However, the monozyg
otic twin correlation was not significantly larger than the dizygotic
twin correlation so that heritability is poorly estimated. Conclusion:
These results are consistent with a genetic regulation of the respons
e to newborn BCG immunization in humans by a mechanism capable of prod
ucing similar responses in identical and nonidentical twins alike.