Immunosuppressive therapies and disease persistence
Immunosuppression is a frequently effective method for controlling
symptoms in many CIDs. It might be argued that if microbial colonization
is the underlying cause, as proposed by the PHM hypothesis, then
immunosuppressive therapies should be harmful. However, if the PHMs are
relatively low virulence microbes and/or the immune responses against
the PHMs are minimally effective or counterproductive, immunosuppression
may have more benefit than harm.
According to the PHM hypothesis, the ineffectiveness of the immune
response against the PHMs in CIDs is supported by the usual persistence
of CIDs. This ineffectiveness could be due to varied factors, including
microbial toxins, the microbes’ antigenic changes and the effects of
heterologous immunity as discussed previously. Chronic PHM exposure or
repeated reinfection could also play a role. The IgE and other immune
responses may be generally protective but perhaps not effective in the
context of colonization by multiple novel PHMs in a westernized
environment.