SPECIFIC IMMUNE SYSTEM BLYMPHOCYTES Immune system diseases Disease
SPECIFIC IMMUNE SYSTEM B-LYMPHOCYTES
Immune system diseases Disease survival mechanisms Non specific immunity Physical & chemical barriers Infectious Disease Inflammatory Non-specific Cellular response Specific immunity Transmissi on Epidemiolog y Vaccination Public Health Immunological surveillance T cells B cells Clonal Selection theory Big picture
LEARNING OUTCOMES • EXPLAIN THE ROLE OF LYMPHOCYTES, B CELLS IN THE IMMUNE SYSTEM • IDENTIFY THE NEED FOR IMMUNOLOGICAL MEMORY • APPLY THE IMPORTANCE OF PRIMARY AND SECONDARY RESPONSES
THIRD LINE OF DEFENCE • SPECIFIC (ONLY ACTS ON PARTICULAR PATHOGEN) • FIRST IMMUNOLOGICAL SURVEILLANCE OCCURS TO FIND/ DISCOVER PATHOGEN • THEN CLONAL SELECTION NEEDS TO OCCUR TO FIND THE CORRESPONDING LYMPHOCYTE TO COMBAT THE PATHOGEN Line of Specific (s) or Mechanism employed Function defenc e non-specific (ns) 3 rd S Antibodies production from B Make antibodies (humoral cells from bone marrow response)and are found in the lymphoid organs (except the thymus) Response by T cells from Cellular immunity but also with thymus gland the regulation of the humoral response
B LYMPHOCYTES (B CELLS) • LYMPHOCYTES RESPOND SPECIFICALLY TO ANTIGENS ON FOREIGN CELLS, CELLS INFECTED BY PATHOGENS AND TOXINS RELEASED BY PATHOGENS. • AN ANTIGEN IS A COMPLEX MOLECULE – RECOGNISABLE AS SELF OR FOREIGN/ NON-SELF • ANTIGEN TRIGGERS PRODUCTION OF ANTIBODIES • ANTIBODY IS A Y-SHAPED MOLECULE WITH A SPECIFIC RECEPTOR (BINDING SITE)
SPECIFIC IMMUNITY ANTIBODY-ANTIGEN INTERACTION • ANTIGEN - ANY AGENT CAPABLE OF ELICITING AN IMMUNE RESPONSE • ISOLATED MOLECULES • MOLECULES ON SURFACE OF CELL OR VIRUS * • A SPECIFIC ANTIBODY MOLECULE WILL BE ABLE TO RECOGNIZE A SPECIFIC (EPITOPE ) ANTIGEN
B CELL ACTIVATION B CELLS PLAY THREE IMPORTANT ROLES IN THE IMMUNE RESPONSE: • THEY PRODUCE ANTIBODIES IN RESPONSE TO SPECIFIC ANTIGENS • THEY PERFORM THE ROLE OF ANTIGEN-PRESENTING CELLS • THEY DEVELOP INTO MEMORY B CELLS.
B CELL ANTIBODIES EACH B CELL CAN A PRODUCE A SPECIFIC ANTIBODY THAT CAN RECOGNISE A SPECIFIC ANTIGEN FROM A PATHOGEN OR TOXIN. THE ANTIBODY WILL BIND TO THE ANTIGEN, FORMING AN ANTIGEN–ANTIBODY COMPLEX. THE ANTIGEN–ANTIBODY COMPLEX HAS TWO MODES OF ACTION: • IT MAY INACTIVATE THE PATHOGEN/TOXIN (NEUTRALISATION), RENDERING IT SUSCEPTIBLE TO PHAGOCYTOSIS. • IT MAY STIMULATE A RESPONSE, RESULTING IN CELL
Agglutination § Antibodies can cause microbes to stick together § This makes it easier for phagocytes to engulf them
Inactivate § Antibodies can bind to pathogen § Causing them to become inactive / rendering them harmless
Neutralisation § Some pathogens make us ill by producing toxins § Some antibodies work by neutralising these toxins
Stimulate cell lysis § The binding of an antibody to the surface of a pathogen can set of a chain reaction with blood proteins, which. . . §. . . causes the pathogen to swell up an burst.
NEED A LITTLE HELP FROM MY FRIENDS. . • B CELLS CAN IDENTIFY SPECIFIC ANTIGENS AND PRESENT THEM TO T CELLS. • T CELLS CAN THEN DESTROY THE PATHOGEN.
* T HELPER CELLS Signal 2 - T cell help B YYY Signal 1 antigen & antigen receptor Th Th 1. T cell antigen receptor 2. Co-receptor (CD 4) 3. CD 40 Ligand
More About T-Lymphocytes Helper T-cells: B-cell Help the humoral response by involvement in the maturation of B cells and by triggering the production of antibodies by B-cells Antigen SIGNAL Helper T-cell
CLONAL SELECTION THEORY • THE BODY HAS A LARGE NUMBER OF LYMPHOCYTES EACH WITH A SINGLE TYPE OF MEMBRANE RECEPTOR SPECIFIC FOR ONE ANTIGEN. Cell division • WHEN A RECEPTOR IS ACTIVATED BY THE BINDING OF AN ANTIGEN, THE LYMPHOCYTE REPEATEDLY DIVIDES RESULTING IN A
SUMMARY SLIDE SPECIFIC DEFENCES IMMUNE SURVEILLANCE • A RANGE OF WHITE BLOOD CELLS CONSTANTLY CIRCULATE MONITORING THE TISSUES. • IF TISSUES BECOME DAMAGED OR INVADED, CELLS RELEASE CYTOKINES WHICH INCREASE BLOOD FLOW RESULTING IN SPECIFIC WHITE BLOOD CELLS ACCUMULATING AT THE SITE OF INFECTION OR TISSUE DAMAGE. • RECOGNITION OF SELF AND NON SELF THROUGH SPECIFIC SURFACE PROTEINS (ANTIGENS) • LYMPHOCYTES RESPOND SPECIFICALLY TO ANTIGENS ON FOREIGN CELLS, CELLS INFECTED BY PATHOGENS AND TOXINS RELEASED BY PATHOGENS.
Summary slide SPECIFIC DEFENCES B LYMPHOCYTES • EACH B LYMPHOCYTE CLONE PRODUCES A SPECIFIC ANTIBODY MOLECULE THAT WILL RECOGNISE A SPECIFIC ANTIGEN SURFACE MOLECULE ON A PATHOGEN OR A TOXIN. • ANTIGEN-ANTIBODY COMPLEXES MAY INACTIVATE A PATHOGEN OR TOXIN OR RENDER IT MORE SUSCEPTIBLE TO PHAGOCYTOSIS. • IN OTHER CASES THE ANTIGEN-ANTIBODY COMPLEX STIMULATES A RESPONSE WHICH RESULTS IN CELL LYSIS. • B LYMPHOCYTES ACTIVATED BY ANTIGEN PRESENTING
SUMMARY SLIDE SPECIFIC DEFENCES IMMUNOLOGICAL MEMORY CELLS • SOME T AND B LYMPHOCYTES PRODUCED IN RESPONSE TO ANTIGENS BY CLONAL SELECTION SURVIVE LONG TERM AS MEMORY CELLS. • A SECONDARY EXPOSURE TO THE SAME ANTIGEN RAPIDLY GIVES RISE TO A NEW CLONE OF LYMPHOCYTES PRODUCING A RAPID AND GREATER IMMUNOLOGICAL RESPONSE. •
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