In this video, Prof Vernon J Louw provides a detailed explanation of the role of plasma cells in the immune system and how their abnormal proliferation leads to multiple myeloma. He explains the process of immunoglobulin production by plasma cells, the concept of polyclonal and monoclonal responses, and how the overproduction of monoclonal antibodies in multiple myeloma can lead to organ damage and increased blood viscosity. Prof Louw also highlights how the presence of these antibodies can be used as a marker of disease activity to monitor treatment response.