  We present an observational study of the Lx vs Lb sigma^2 relation for
early-type galaxies in the Coma cluster based on the XMM-Newton survey data.
Compared to a similar relation for a sample dominated by field early-type
galaxies, the Coma cluster galaxies show a flatter slope. Our calculations show
that adiabatic compression produces a flattening in the Lx vs Lb sigma^2
relation that is in remarkable agreement with the observed effect. Our scenario
is further supported by the observed compactness of the X-ray emission of Coma
galaxies.
