Arellano and Lonial difference in the ratio of DC1:DC2 between CSF regimens. This ﬁnding supports the hypothesis that higher numbers of DCs in the graft might be associated with prolonged survival of NHL patients after autologous transplantation (Gazitt et al 2006). Further studies in larger populations of patients are merited. More is known about the effects of G-CSF than the effects of GM-CSF on post-transplant immune reconstitution. Volpi and colleagues reported on the effects of G-CSF admin- istration in the post-transplant setting among 43 patients with acute leukemia who received T-cell depleted peripheral blood progenitor cell transplants from HLA haplo-identical related donors, compared to a cohort of 36 patients with acute leukemia who did not receive G-CSF after transplanta- tion. They found signiﬁcantly delayed recovery of Th1-type CD4+ T-cells (low IL-4 and IL-10, and high IL-12 receptor expression), a higher proportion of CD4+ T-cells with a Th2 phenotype (high levels of IL-4 and IL-10, and low levels of IL-12 receptor expression), and impaired production of IL-12 by dendritic cells, compared to patients who did not receive post-transplant G-CSF. T-cells from recipients of post-trans- plant G-CSF had signiﬁcantly decreased in-vitro reactivity to fungal pathogens compared to T-cells from patients who did not receive post-transplant G-CSF. This ﬁnding suggests an increased susceptibility to opportunistic infections in the G-CSF treated cohort, given that Th1-responses are necessary for anti-fungal protection (Volpi et al 2001). The effect of G-CSF on post-transplant immune reconstitution appeared to be dependent on G-CSF’s inﬂuence on DC maturation and differentiation; given that administration of G-CSF following transplantation favored the appearance of IL-12-deﬁcient DC which polarize T-cells toward Th2 responses. Fagnoni reported a similar effect of post-transplant G-CSF in children (Fagnoni et al 2004). Ringden et al performed a retrospective analysis to determine the role of post-transplant treatment with G-CSF in patients with AML and acute lymphocytic leukemia (ALL) who received allogeneic BMT or peripheral blood grafts. They found that prophylactic, post-transplant treatment with G-CSF led to a higher risk of acute and chronic GVHD, higher transplant related mortality, and decreased overall survival and leukemia-free survival rates in patients who received BMT only. Post-transplant G-CSF led to faster engraftment of absolute neutrophil count but slower engraftment of platelets in transplant recipients irrespective of the type of graft (Ringden et al 2004). These findings suggest that post-transplant administration of G-CSF may cause an imbalance in dendritic cell content or function, resulting in impaired cellular immunity in the early post-transplant period. This may lead to an increase 18 in the incidence of GVHD (Fagnoni et al 2004). Current guidelines support the use of colony stimulating factors for mobilization of autologous and allogeneic grafts and after peripheral blood progenitor cell transplantation in the autologous setting only (Smith et al 2006). Further studies are needed to support the addition of GM-CSF after allo- geneic transplantation. GM-CSF may improve antibody- dependent cell-mediated cytotoxicity The anti-CD20 antibody, rituximab, used alone or in com- bination with chemotherapy, is an established treatment for non-Hodgkin’s lymphoma (NHL) (Cvetkovic and Perry 2006). Augmenting the expression of CD20 antigen on the tumor cells may increase the cell kill and therefore increase the effectiveness of the antibody (Venugopal et al 2000). Pre- liminary data suggest that GM-CSF can up-regulate the CD20 expression on lymphoid B cells in vitro, but these results have not been reproducible in vitro nor in vivo (Venugopal et al 2000; Chow et al 2001; Yagci et al 2005). Venugopal and colleagues performed experiments on cells from patients with chronic lymphocytic leukemia (CLL) where CLL cells were cultured with cytokines and the expression of CD 20 on the surface of the CLL cells was measured before and after cytokine exposure. They found a statistically signiﬁcant up-regulation of CD20 antigen expression on CLL cells after culture with GM-CSF, IL-4, or TNF-alpha. Flow cytometry evaluation revealed an increase in ﬂuorescence intensity as well in the percentage of cells expressing the antigen (Venugopal et al 2000). This led to further studies which have revealed promising, but incon- sistent results. Olivieri and his group showed the feasibility of rescuing patients with NHL relapsing after autologous transplantation with a regimen containing rituximab, CHOP chemotherapy and GM-CSF. They reported a 75% overall response rate (60% complete remission, and 15% partial response) among 20 patients with aggressive NHL who relapsed after autologous transplantation (Olivieri et al 2005). Rapoport and colleagues reported promising results utiliz- ing post-transplant rituximab and GM-CSF after autologous transplantation among a group of patients with advanced NHL and Hodgkin’s disease (Rapoport et al 2002). However neither up-regulation of CD20 antigen, nor a change of the proportion of CD20 positive cells was observed after culture with GM-CSF in a study by Yagci et al (2005) on cells from 18 patients with CLL. Biologics:Targets & Therapy 2008:2(1)