Lymphocyte activation under the microscope
The adaptive immune system has evolved to offer immunological memory in order to more effectively protect against pathogens. For a protective immune response to be elicited, a series of complex steps involving activation and differentiation of immune cells are involved. Although B lymphocytes and their antibody production are very important for the eradication of many diseases, the mechanism underlying the in vivo activation of these cells is poorly understood. The objective of the EU 'In vivo study of primary B cell responses' (PBC-BS) project was to understand the factors that are involved in lymphocyte activation in vivo and how these ultimately affect immune responses. By taking advantage of new microscopy techniques, consortium partners were able to visualise the actual process of lymphocyte activation in a living organism. They found that at the beginning of an immune response a specialised subtype of T lymphocytes – known as natural killer T (NKT) cells – gets activated by macrophages in the lymph nodes and causes a local response that recruits several types of immune cells. For the development of an adaptive immune response, team members found that these NKT cells interacted with B cells at the lymph nodes which prompted activation and antigen-specific antibody secretion by B cells. Overall, the PBC-BS project provided a comprehensive insight of the cellular interactions that take place in the lymph nodes at the beginning of immune responses. The discovery of NKT cells as key players in immunity offered a new perspective on how the human body combats disease. NKT cells and their mechanism of activation may be exploited for the development of novel vaccination strategies.
