The temporal sequence of infections, especially initial and early ones, is crucial to the development of patterns of immune reactivity as prior contacts with other antigens may have induced cross-reactive T-helper cells competing with T reg s. As a consequence T reg s normally induced by the second pathogen may be marginalized or even eclipsed. The latter phenomenon, also known as lateral inhibition, has many parallels in biology, particularly in neurology. The locking of an immune response into an eclipsed state seems to involve an active deletion of clones of T-cells occurring as a result of reinfections or reactivations [28] . In the case of MS, infections such as those with HHV-6 [30, 31] and, possibly, with CP [12, 26] occurring before or at the time of initial or reactivated EBV infection could have such an effect.