Analysis of the cellular and tissue specificity of gene expression, using public gene expression databases [54-56], indicated that genes encoding CD48 (Cd48), membrane-spanning 4A6B and 4A6C (Ms4a6b and Ms4a6c), epidermal growth factor-like receptor-like protein 1 (Emr1), and interferon-induced 47 kDa protein (Ifi47) were most probably originating from donor lymphoid cells, whereas other early arthritis genes (Table 2) were related to the activation of the innate immune system (represented by macrophages, dendritic cells, and cells of myeloid lineage) of recipient BALB/cSCID mice. This evidence concerns the gene CD48 and Arthritis.