The cellular reactions to defatted tubercle bacilli are complex and like those to heat-killed whole tubercle bacilli.

The firmly bound lipid, when removed from these organisms, is non-acid-fast; it contains an hydroxy acid which is acid-fast and a polysaccharide, which is not.

This hydroxy acid gives rise to foreign body giant cells and the tissues eventually become infiltrated with eosinophiles.

The polysaccharides, both from the defatted bacilli and from the unfilterable lipid, call neutrophiles from the blood stream.

The reactions to the unfilterable lipid include those of both its constituents.