Intro to B Cells & Development PDF

WELCOME! BMS 545 IMMUNOLOGY OCTOBER 16, 2024 ANNOUNCEMENTS  No more true “homework” until Module 4  I will post an exam debrief video once all students have taken the exam so I can talk more freely  I will post CBL answers once I am done grading!  Office hours back to normal!  Tuesday 4...

WELCOME! BMS 545 IMMUNOLOGY OCTOBER 16, 2024 ANNOUNCEMENTS  No more true “homework” until Module 4  I will post an exam debrief video once all students have taken the exam so I can talk more freely  I will post CBL answers once I am done grading!  Office hours back to normal!  Tuesday 4-5 pm virtual  Thursday 4-5 pm in-person (316J) DID EVERYONE HAVE A GOOD FALL BREAK? ANYTHING EXCITING? ADAPTIVE IMMUNITY & B-CELL REVIEW  OBJECTIVES  Describe how adaptive immune system differs from innate & unique features of the adaptive immune system  Describe the function & role of each adaptive immune cell* & be able to identify them based on generalized picture, description of function or histology  Describe how B cell graduates can be differentiated & where they can be found during gestation  Recognize & describe the microenvironments where adaptive immune cells* mature & the adaptive immune response develops  Identify the primary & secondary immune organs in vertebrates & describe their function in relation to the adaptive immune system & adaptive immune cells*  Describe the environment where B cells develop  Describe how bone marrow stromal cells play a role in driving B cell development *With a focus on B cells & plasma cells! INNATE VS. ADAPTIVE IMMUNITY  PURPOSE OF ADAPTIVE IMMUNE SYSTEM  Steps in when innate immune system fails  Comprises immunological memory- ability to recognize & remember specific pathogens via their antigens  Produces antibodies  Humoral immune response- “fluids” that prevent or defend against microbial attack  Antibodies recognize and bind to microbial epitopes:  to prevent microbial spread by immobilization (agglutination)  prevention of microbial attachment to host cells (neutralization)  promotion of microbial phagocytosis and clearance (opsonization)  targeting of microbial destruction by soluble molecules (complement) or by leukocytes  Cell-mediated immunity- leukocytes destroy invading cells The Lymphocytes LYMPHOCYTES “Relating to lymphatic system” Lymphocytes produced in bone marrow travel through lymphatic system and further differentiate/ proliferate within lymphoid tissue (lymph nodes, thymus, spleen)  INTRO TO B-CELL  DEVELOPMENT Hematopoietic stem cells in bone marrow become common lymphoid precursor (CLP) lineage  Differentiates in thymus (T- cells)  Remains in bone marrow (B-cells)  B-cell “graduates” in each of these groups can be differentiated by:  extent of their “education”  arrival & departure from B.M.  diversity or “repertoire” of BCRs  geographic distribution in body  nature of responses to LYMPHOCYTES  Lymphocytes are defined by where they undergo “basic training” & by the type of receptors they display on their cell surfaces: TCR (T cells & NKT cells), BCR or immunoglobulins (B cells), or neither (NK cells)  Bone marrow-derived cells:  Not all lymphocytes of bone marrow origin are destined for thymic education  Certain lymphoid cells remain & develop in the bone marrow & are precursors of immunoglobulin-producing lymphocytes  B cells- synthesize immunoglobulin and display it on their surfaces, where it functions as their BCR  Plasma cells- derived from differentiated, mature B cells and both synthesize and secrete immunoglobulin  B-CELL  Do not migrate to the thymus but develop within the bone marrow  Arise from HSCs in the bone marrow  Two distinct lineages: B-1 & B-2 cells  B-1 cells (first to develop embryologically)- self-renewing population that dominates the plural & peritoneal cavities  B-2 cells (conventional) arise during & after the neonatal period, are continuously replaced from the bone marrow, & are widely distributed throughout the lymphoid organs & tissues  Each B cell is specific- it produces immunoglobulin of only one antibody specificity that recognizes only one epitope.  It is the extreme diversity among B cells, each producing a single form of immunoglobulin, that generates the overall diversity of the immunoglobulin (or antibody) response Chapter Opener B-CELLS!! B-CELL LINEAGE OVERVIEW  In humans, progenitors of immunoglobulin-producing cells are found during gestation:  3rd week- yolk sac  8th week- fetal liver  ~12th week- bone marrow  Called “bone marrow–derived lymphocytes” or B cells because this is where most of these cells differentiate  B cells are cells that synthesize immunoglobulin & display it on their surfaces as their BCRs  Once they become activated, they differentiate into plasma cells which can then synthesize AND secrete their BCR as an antibody  PLASMA CELL  Derive from terminally differentiated B cells & are immunoglobulin-producing AND immunoglobulin- secreting cells  Characterized by basophilic cytoplasm, a nucleus that has a stellate (starlike) pattern within it, and non-staining Golgi  Cease to use immunoglobulin as a membrane receptor & instead secrete it into the fluids around them  Secreted immunoglobulin known as “antibodies”  With increased size & metabolic activity, are factories that produce large quantities of immunoglobulin during their short life span of