Human beings live in an environment endemic
to various diseases. Under such conditions, some
individuals are susceptible to certain diseases while
most are resistant to those diseases. This raises many
questions. One such question is whether the person
who is susceptible is genetically different from the
person who is resistant to the disease? Similarly, in
a family, one of the parents may be affected with a
particular disease (e.g. diabetes); among the children
born to the parents, if one child (younger one)
develops the disease and the other child (elder one)
does not, the question arises why did the younger
one develop the disease and the elder did not, when
both of them were living together with the affected
parent. This raises the possibility of the disease
being inherited from parents. If genetic factors play
a major role in disease susceptibility or resistance,
in what way are they associated with the disease
development? Do they control the immune response
to an antigen and/or pathogen? Do they play a role
in the immune mechanism of susceptibility or
resistance to disease? This article gives an account
of disease susceptibility or resistance in pulmonary
tuberculosis in the context of the host genetic factors,
i.e. HLA (Human Leucocyte Antigens) and non-
HLA genes and their gene products
