The CD20-homolog Ms4a8a was identified as a novel molecule of tumor-associated macrophages directly enhancing tumor growth. In addition, Ms4a8a is expressed in typical M2-dominated pathologies as late stage Trypanosoma congolense and Taenia crassiceps infections. For its induction a complex stimulation with pro- and antiinflammatory mediators is necessary. In this study we analysed how forced over-expression of Ms4a8a modulates the TLR4 response of RAW264.7 macrophages. We used microarrays to assess gene regulatory functions of Ms4a8a in Raw264.7 macrophages Overall design: A recombinant Ms4a8a cDNA was amplified by PCR (primer: Ms4a8a-SpeI-fw 5’ATCGAATTCACTAGTAGCAAAGAGTTGGGAACCGGAGCAAGA3’ and Ms4a8a-NotI-rv: 5’ATATGCGGCCGCTAGAGCATCTTTAT3’) from Ms4a8a cDNA RZPDp981B0530D (IMAGE ID 905005), purified on agarose gel and subcloned after digestion with SpeI and NotI restriction enzymes into the expression vector pEF6/V5-His Topo (Invitrogen) according to standard molecular biology protocols. After confirming sequence identity, we transfected RAW264.7 cells with Ms4a8a vector DNA using Lipofectamine 2000 (Invitrogen) transfection reagent. Transfectants were selected by resistance to blasticidin (Invitrogen). Raw264.7Ms4a8a clone K8 with recombinant Ms4a4a expression were propagated. As a negative control, a vector-transfected RAW264.7mock (clone K3) was selected under parallel culture conditions.