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.