Rituximab (anti-CD20) is an anti-CD20 chimeric monoclonal antibody used to treat certain autoimmune diseases and types of cancer.In Vitro: Rituximab (anti-CD20) inhibits the proliferation of stimulated human B cells, which is associated with a relative increase of B cells with an activated naive phenotype. Aside from this population shift, there are no major changes in phenotype or cytokine profile of the various B-cell subsets. B cells stimulated in the presence of rituximab induces stronger T-cell proliferation, compared to B cells stimulated in the absence of rituximab. All lymphoma cells tested are equally sensitive to antibody-dependent cell-mediated cytotoxicity (ADCC), antibody-mediated phagocytosis of tumor cells, and rituximab-induced apoptosis. Rituximab (anti-CD20) induces high CDC killing of follicular lymphoma cells[2].In Vivo: A single injection of rituximab or the murine anti-CD20 Ab 1F5, given i.p. 1 day after the tumor, cures 100% of the animals. Depletion of either NK cells or neutrophils or both in tumor-injected animals does not affect the therapeutic activity of the drug. Similarly, rituximab is able to eradicate tumor cells in athymic nude mice, suggesting that its activity is T cell independent.