'Travels of a mature B cell:From Immigration to B-Exit': The Inaugural Lecture of Professor Kai-Michael Toellner

You are invited to attend the inaugural lecture of Professor Kai-Michael Toellner.

In H. G. Wells’ novel The War of the Worlds, the invading army of Martians, just about to enslave and exterminate humankind, is finally overcome by earthly microbes to which they have no immunity - “slain, after all man's devices had failed, by the humblest things that God, in his wisdom, has put upon this earth". This summer 50 years ago, the coming home of astronauts from the first moon landing showed that being overcome by alien pathogens is also a concern for humankind. Not only that: planet earth provides vast biotopes and ecological niches where new microbes and variants of established pathogens evolve all the time.

Why do we not all die from them like Martians? Fact is that our immune system can adapt to virtually any new structures our bodies encounter – whether they are alien or earthly - and build defences against them. Surviving a new infection for more than a few days makes our immune system develop adaptive immune cells that will express highly specific receptors specifically interacting and neutralizing foreign invaders. This will lead to extermination of the specific pathogen and to long-lasting immunity. This is why we are not infected by the same pathogen twice – our immune system develops long-lasting immunity. Vaccination mimics this process, inducing specific immunity that can last as long as we live.

The main mechanism how vaccination provides specific immunity is the induction of antibodies – receptors that specifically stick to critical surface structures on pathogens. B cells are the cells that produce these antibodies. They do this by entering lymphoid tissues, interacting with pathogen antigens, and mutating their antibody receptor genes and retesting them on the same antigens. A couple of weeks of this process of Darwinian evolution on a molecular scale generates antibodies that will stick to pathogens with high affinity and specificity. These specific antibodies are then produced and confer immunity for many years. Some B cells will become long-lived memory cells that will be ready to reenter responses should pathogen variants emerge.

I will show how B cells develop in lymph nodes in response to foreign antigens. How they travel through lymph nodes and interact with pathogens and other cells, and how they finally emerge from lymph nodes as antibody forming cells or as memory B cells that provide us with long-term immunity.