The body is very careful to protect the lungs. After all, oxygen is arguably any cell's most pressing need. Therefore, rather than risking the damage that a full scale immune response might bring, the body tends to form cysts of non-nutritious scar tissue around the invading organism. This both starves out the organism and allows the body to bring all of its immune response to bear without fear of dammaging healthy tissue. Any organism wishing to live here must deal with this problem.