الفهرس 
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Abstract
The diminution of hearing with aging process is always sensorineural. It is
the auditory manifestation of a biological process involving all the tissues of the
body. Both sexes can be affected but the true sex incidence has not been reliably
established. The speed of onset of degenerative changes in the ear is determined
by genetic factors, physical stress and noise exposure during a normal life span.
The onset of presbycusis is earlier in the urban population than of the rural
population.
An interesting question is why some people develop sensorinerual hearing loss
with aging and others do not, the explanation could be related to their immunity
system. Because HLA is a genetic marker of the immunity system, we
investigated the patients of SNHL with aging process and normally hearing senile
persons by tissue typing HLA class I aiming to discover a relation between HLA
and the disease.
HLA system is known to have an association with certain disease states.
Several hypothesis have been advanced to explain this relation. The first holds that
HLA antigens are merely markers for immune response or suppressive genes. The
second suggests that HLA antigens act as receptors for etiologic agents. The third
is that molecular mimicry. The last is that the expression of class II on the surface
of the cells that do not normally express it , is responsible for disease.