The formation of cysts is in part triggered by the pressure of the host immune system. The bradyzoites (also called "bradyzoic merozoites") are not responsive to antibiotics. Bradyzoites, once formed, can remain in the tissues for the lifespan of the host. In a healthy host, if some bradyzoites convert back into active tachyzoites, the immune system will quickly destroy them. However, in immunocompromised individuals, or in fetuses, which lack a developed immune system, the tachyzoites can run rampant and cause significant neurological damage.The parasites survival is dependent on a balance between host survival and parasite proliferation. T. gondii achieves this balance by manipulating the hosts immune response, reducing the hosts immune response, and enhancing the parasites reproductive advantage. Once it infects a normal host cell, it resists damage caused by the hosts immune system, and changes the hosts immune processes.As it forces its way into the host cell, the parasite forms a parasitophorous vacuole (PV) membrane from the membrane of the host cell. The PV encapsulates the parasite, and is both resistant to the activity of the endolysosomal system, and can take control of the hosts mitochondria and endoplasmic reticulum.When first invading the cell, the parasite releases ROP proteins from the bulb of the rhoptry organelle. These proteins translocate to the nucleus and the surface of the PV membrane where they can activate STAT pathways to modulate the expression of cytokines at the transcriptional level, bind and inactivate PV membrane destroying IRG proteins, among other possible effects.
The effect can produce a minor size variation to an extremely large breast asymmetry. Breast hypertrophy is classified in one of five ways: as either pubertal (virginal hypertrophy), gestational (gravid macromastia), in adult women without any obvious cause, associated with penicillamine therapy, and associated with extreme obesity. Many definitions of macromastia and gigantomastia are based on the term of "excessive breast tissue", and are therefore somewhat arbitrary. A total of 115 cases of breast hypertrophy had been reported in the literature as of 2008. Virginal breast hypertrophy
When gigantomastia occurs in young women during puberty, the medical condition is known as juvenile macromastia or  juvenile gigantomastia and sometimes as virginal breast hypertrophy or virginal mammary hypertrophy. Along with the excessive breast size, other symptoms include red, itchy lesions and pain in the breasts. A diagnosis is made when an adolescents breasts grow rapidly and achieve great weight, usually soon after her first menstrual period. Some doctors suggest that the rapid breast development occurs before the onset of menstruation.Some women with virginal breast hypertrophy experience breast growth at a steady rate for several years, after which the breasts rapidly develop exceeding normal growth. Some adolescent females experience minimal or negligible breast growth until their breasts suddenly grow very rapidly in a short period of time. This may cause considerable physical discomfort. Women with VBH often experience an excessive growth of their nipples as well.