MMP9 and myeloid sarcoma: When restricting the attention to MMP-9, assumed to be the most important MMP immune effector implicated in MS pathogenesis, it is possible to note that it is secreted as inactive forms (the zymogen pro-MMP-9 multimers and monomers and pro-MMP-9 associated with lipocalin) and its activity is related to at least two activation forms (the N-terminal truncated 82 kD form; the N-and C-terminal truncated 65 kD form).