Lecture 22: Cellular Interactions and Trafficking - B Cells Flashcards
Recall the key learning objectives from this subject (Lecture 22: Cellular Interactions and Trafficking - B Cells)
Differ between the development process of B1 and B2 cells.
B1 cells are a sub-class of B cell lymphocytes that are involved in the humoral immune response. They are not part of the adaptive immune system, as they have no memory, but otherwise, B1 cells perform many of the same roles as other B cells.
Describe marginal zone B cells.
Found mainly in the marginal zone of the spleen and serves as a first line of defense against blood-borne pathogens, as the marginal zone receives large amounts of blood from the general circulation.[24] They can undergo both T cell-independent and T cell-dependent activation, but preferentially undergo T cell-independent activation
Describe follicular B cells.
Recall B cell responses.
Recall how B cell activation leads to differentiation.
Mature, naïve B cells require two signals to be activated and differentiate into antibody-secreting cells: (2)
Describe the concept of linked recognition.
Linked recognition is a process by which a B cell is optimally activated by a helper T cell that responds to the same, or physically associated, antigen.
However, the peptide recognized by the TFH cell is likely to differ from the protein epitope recognized by the B cell’s antigen receptor.
Recall how inked recognition is important for B cells.
If a B cell encounters its antigen, either on a follicular dendritic cell (FDC) or a macrophage, it increases expression of CCR7 and migrates toward the border with the T-cell zone (third panel). T cells activated by antigen-presenting dendritic cells induce expression of CXCR5 and migrate to this same border, where linked recognition induces further B-cell proliferation.
Also, linked recognition works to preserve self-tolerance, since autoreactive antibodies will arise only if self-reactive TFH and self-reactive B cells are present at the same time.
Recall how antigen reaches naiive B cells.
Macrophages residing in the lymph node subcapsular sinus (SCS) express complement receptors 1 and 2 (CR1 and CR2, respectively).
Opsonized antigen arriving from the afferent lymphatics binds to CR1 and CR2 on the surface of SCS macrophages. Instead of being completely degraded by these macrophages, some antigen is retained on the cell surface, where it can be presented and transferred to the surface of follicular B cells. B cells are then able to transport the antigen into the follicle, where it can be trapped on the surfaces of follicular dendritic cells.
How do B and T cells find each other?
Naïve B cell recognizing cognate antigen leads to________________, attracting it toward the T cell zone. T cells activated by antigen express ____________, migrate towards the follicle, and encounter B cells.
Naïve B cell recognizing cognate antigen leads to CCR7 upregulation, attracting it toward the T cell zone. T cells activated by antigen express CXCR5, migrate towards the follicle, and encounter B cells.
Describe germinal centre.
Describe affinity maturation by somatic hypermutation.
Describe isotype switching.
