  We give an extension of the two-component KP hierarchy by considering
additional time variables. We obtain the linear $2\times 2$ system by taking
into consideration the hierarchy through a reduction procedure. The Lax pair of
the Schlesinger system and the sixth Painlev\'e equation is given from this
linear system. A unified approach to treat the other Painlev\'e equations from
the usual two-component KP hierarchy is also considered.
