3.Humoral immunity; B-lymphocytes Flashcards
Humoral immunity =
antibody-dependent specific immune
defense (B-cell defense)
what happened when an antigen enters
When an antigen enters the body it is immediately recognized by B-lymphocytes containing the proper antigen-binding receptor. The activated lymphocytes within this clone then begin to divide rapidly.
plasma cells: what is it
Contain more cytoplasm and are larger than B-
cells
plasma cells: produce and secrete
Produce and secrete antibodies identical to the
receptors on the B-cells that recognized and
bound the antigen epitope.
plasma cells: cell life time
Plasma cells die after a few days of intensive
antibody production, since the antibodies are proteins
Plasma cells: how they are formed
When a lymphocyte clone is activated by its antigen epitope, most of the cells are differentiated into plasma cells
Memory cells: what are they and what do they do
Do not participate in the immediate attack on
the antigen, but continue to live for months and years after the antigen has been eliminated, ready for stimulation if the antigen is encountered again.
Primary response:
On first exposure to an antigen, several days elapse before formation of antibodies begins. The antibody formation is then moderate. This antibody production is the primary response.
Primary response: delay, why?
The delay is mainly due to the time required for the lymphocyte of the correct clone to come in contact with the antigen. The lymphocyte of this clone must also undergo a proliferation phase before a substantial antibody production can begin.
secondary response: what is it
When a previous encountered antigen reenters the body, the antibody formation changes character, resulting in the secondary response.
how to get further activation for clonal expansion
For further activation to occur in the form of clonal expansion and substantial antibody synthesis, the B-cell In most cases needs the assistance of a T-cell.
how to make the antigen get recognised by the t-cell for clonal expansion
The complex formed between the antigen and the membrane receptors of the B-cells is transported into the cell (endocytosis) then broken down to antigenic epitopes then carried back to the surface of the cell, with the B-cell’s MHC class II proteins.
B-cell maturation first phase
pre-B-lymphocytes mature and become so-called virgin-B-lymphocytes. On the surface of each virgin-B-lymphocyte there will be an IgG-like molecule appearing against a certain possible antigen structure
B-cell maturation 2nd phase
begins when the cell get into the blood ciculation. If there is an APC presented Ag against which the virgin B-Ly has an Ig structure, then this virgin-lymphocyte binds the antigen and it gets activated. Cell signals (interleukins) expressed during binding activateB-lymphocytes. The activated B-lymphocyte can settle in the B-dependent zones of the secondary lymphatic organs, where it goes through blastic transformation.
Following Ag stimulus, the efficiency and potency of the immune respons will decrease due to:
Elimination of Ags (which reduces the Ag stimulus)
The activated Lys will die or converted to memory cell
