Th2, by making anti-inflammatory cytokines, may help rein in inflammation. But, beneficial as they are, Th1 and Th2 can cause problems. In particular, the cytokines produced by one or the other can sometimes alter the balance of the immune response and bring about inappropriate reactions. For example, if there is a high level of Th2 cytokines in the circulation and in the tissues, perhaps leftover from an earlier infection, the response to a new infection can be pushed toward Th2 even though Th1 would be more appropriate. This clearly happens.
Many researchers maintain that the same occurs in humans.
Also, inappropriately polarized Th1 and Th2 responses appear capable of causing damage of their own. In contrast, conditions such as lupus and allergies may be exacerbated by a predominant Th2 form of immunity. Still, most if not all researchers would probably agree that some degree of interplay between these types of immunity does occur in response to HIV, just as it does in other infectious diseases. Thus, there are numerous theories as to what affect Th1 and Th2 interaction may have in HIV disease, but no consensus as to what may be occurring. According to this hypothesis, the body's initial response to HIV is predominantly, perhaps even entirely, Th1 in nature.