For example, a sample can include cells such as fibroblasts, endothelial cells, peripheral blood mononuclear cells, haematopoietic cells, or a combination thereof.Probe to Detect Retroviral Antigen in a SampleDetecting, diagnosing, monitoring or managing an XMRV-related neuroimmune disease or XMRV-related lymphoma in a subject can be based upon a probe that binds at least one gammaretrovirus antig