A New Micro-Organ Hosting Memory B Cells Discovered in Our Immune System

One of the most intriguing questions about the immune system was where memory B cells gather. This question was answered in August 2018 by a study published in Nature'as the journal. Researchers at Australia's Garvan Institute of Medical Research discovered, in the human immune system, a new micro-organ . This discovery may pave the way for an effective cancer vaccine to be developed.

Researchers recorded all immune system components in mice in real time using high-resolution 3-dimensional microscopy. They discovered thin, smooth structures on the surface of lymph nodes. These structures were dynamic and became visible only when the mouse fought the same infection a second time. They were also found in lymph nodes from people fighting the same infection for a second time. Researchers considered them a new micro-organ and named them subcapsular proliferative foci (SPF). Using two-photon in vivo microscopy, they identified immune cells of the memory B-cell type gathered in these structures.

The newly discovered micro-organ was found to be responsible for rapid immune responses and storing B lymphocytes.

What Is a B Cell / Lymphocyte?

B cells are lymphocytes that play a major role in the adaptive immune system'shumoral response. These cells were first identified in birds in the 1960s. B is an abbreviation derived from the bursa of Fabricius, the organ where these cells mature in birds. The bursa of Fabricius is an avian organ and is absent in mammals.

The human body produces millions of different B-cell types every day, each carrying on its membrane a specific receptor protein capable of binding a particular antigen. Millions of B cells circulate in human blood and lymph without producing antibodies. When a B cell encounters an antigen and receives an additional signal from a helper T cell , it differentiates into one of the two B-cell types described below. B cells may transform directly into one of these cell types or do so after an intermediate step.

• Plasma B cellsproduce antibodies that help destroy antigens by binding them and making them easier targets for phagocytes. 
• Memory B cellsform specifically against antigens encountered during the first immune response and survive a long time. They can respond rapidly when their corresponding antigen is encountered again.

What does this study mean for us?

• A new micro-organ was discovered in the immune system. It was observed to be the site where memory B cells gather.
• Until now, one of the main aims of vaccines has been to generate and activate memory B cells. Discovery of subcapsular proliferative foci may improve understanding of how memory B cells become fighter plasma cells and make this process more effective.
• This discovery may make it possible to enhance secondary antibody responses and cancer vaccine effectiveness.