Presentation on theme: "Part I: Fundamentals of Immunology Part II: The Role of Genetics in Immunosuppression John Ryan, Ph.D. Professor, VCU Department of Biology 1."— Presentation transcript:
Part I: Fundamentals of Immunology Part II: The Role of Genetics in Immunosuppression John Ryan, Ph.D. Professor, VCU Department of Biology 1
3 My shameless recruiting plug… URMs represent 25% of the U.S. population The number of URMs receiving science and engineering PhDs increased 400% from …. But this is still less than 5% of the PhDs awarded VCU has a URM population of approximately 25% in Biology, Chemistry, and related fields. We are committed to encouraging their participation in research.
The Basic Immune Response 4 B APC Tissue Lymph Node Blood B B B B Th
Immunity: The Game 5 Antigen Table Lymph Node Table T cells B cells Antigen Presenting cells
Fundamentals of Asthma Pathogenesis John Ryan, Ph.D. Professor, Biology Department Virginia Commonwealth University
Asthma Pathophysiology Allergic asthma begins as an acute reaction, with mast cells driving bronchoconstriction, coughing, tissue swelling, and clogging of the small lower respiratory tract airways with mucus. The result is air-trapping. White blood cells can be recruited. Chronic asthma is maintenance of this inflamed condition, where the infiltrating white blood cells remain in the lung due to constant allergen exposure. While the response is similar to the acute asthma, the severity grows. Airways can become totally occluded with mucus. Damage to the epithelium leaves the bronchioles hyperresponsive, with bronchoconstriction following many chemicals or irritants. Bacterial and viral infections can follow, and their eliciting a strong Th2 response worsens the asthma. Rhinovirus in particular causes asthma exacerbations in children. Th2 B Mast Cell Ag Inflammatory mediators causing cells to invade, airways to be hyperresponsive
Tissue sections from pt who died of allergic asthma. MP represents mucus plug in airway. Panel B shows eosinophilic infiltration around the lumen of the airway (L). Asthma Pathology Recall that Fαr 4
Global asthma rates Nature, 2011 Oddities include Puerto Rico, with asthma rates of 30% among children, 3X higher than other Hispanics, even when living in the U.S. mainland. By comparison, Mexican Americans have very low asthma rates.
Why is asthma so common? The Hygiene Hypothesis Because the increase in asthma in particular is most overt in developed western nations, and fairly uncommon in third world countries, one theory has received much support. Helper T cells (Th) organize the immune response. A specialized form of helper T cells, called Th2, promote allergic disease. Th2 cells appear to develop in the absence of significant bacterial infection. Since modern countries have protection from infection, this may be increasing the Th2 response in a way that is pathological. Th0 Th1 Kill intracellular pathogens Th2 Kill extracellular pathogens Bacterial products Parasitic infection Th2 Asthma Little bact. exposure Bateria + Urban poverty?? Asthma Th2 Protective Pathological
Therapeutic Strategies for Treating Allergic Disease Avoidance of allergens. Allergen Immunotherapy. Accomplished by injecting Ag in hopes of including Th2 cell anergy or Th1 responses to shift balance toward Th1/IgG production. Allergen Desensitization involves slowly injecting the patient with an increasing dose of the antigen over a period of hours. This appears to tolerize the mast cells to the antigen. This is mostly used to treat patients with drug to which they are reactive (e.g. oxaliplatin) Pharmacologic: Bronchodilator/Vasoconstrictors, like albuterol for asthma; epinephrine for systemic anaphylaxis. Antihistamines (anti-H1) used to treat rhinitis, urticaria. (Claritin) Leukotriene inhibitors for asthma (Singulaire). Costicosteroids for asthma, rhinitis, eczema. (Nasonex) Cromolyn sodium for rhinitis and asthma.(Nasocrom) New therapy with an anti-IgE blocking antibody appears to block mast cell activation (Xolair).
Effect of HMG-CoA reductase inhibitors (statins) on mast cells: Genetic Background Matters 12
Mevalonic Acid Pathway
17 Studying the effects of Fluvastatin on mast cells from different genetic backgrounds C57BL/6 129/Sv Th1-skewed immune response Th2-skewed immune response Bone marrow derived mast cells
Studying the effects of Fluvastatin on mast cell function and survival Bone marrow-derived mast cells IgE+/- Fulvastatin 16hrs Antigen Supernatants collected after 16 hours Measure cytokines by ELISA 18
Th2 Genetic Background can Yield Resistance to Fluvastatin
Mevalonic Acid Reverses the effects of Fluvastatin
Fluvastatin Induces Mast Cell Death % Dead Cells Fluvastatin ( M)
Fluvastatin Suppresses Mast Cell Migration
Conclusions Lyn Syk SOS Vav1 Ras GTP MAPK (ERK1/2/JNK/p38) FcЄRI LAT1 SCF SOS Grb2 Ras GTP Ag Y Y C-KIT MAPK (ERK1/2/JNK/p38) Fluvastatin treatment in C57BL/6 strain Production of inflammatory factors Cell survival Migration/adhesion
The Ryan Lab,
The effect of Fluvastatin on IgE receptor signaling C57BL/6 Cells
Asthma (from ALA Report, 2012) A chronic inflammatory condition of the lungs that causes difficulty breathing. Not a form of COPD, since it is reversible. Epidemiology data of interest: Nearly 26 million Americans have asthma, of which 7 million are children. Asthma rates nationally rose 59% from Total direct health care costs are approximately $16B annually. Highest rate is among 5-17 year-olds. Most common chronic illness of kids. Among children, asthma is slightly more common in boys – but among adults, asthma is about 50% more common in women 3388 people died from asthma in 2009, but the death rate has been declining steadily for 10 years. Major negative predictors for asthma death include: older, female, african- american or Puerto Rican. Death rate for Americans >65yo is about 5X higher than for teenagers. Issues that exacerbate asthma include 2 nd hand smoke and obesity, either of which increases asthma incidence 2-fold. A number of genetic polymorphisms predispose to asthma severity or incidence. These include immune response genes that predispose to allergy and other issues like beta-adrenergic receptor polymorphisms that decrease drug responsiveness.
Allergic vs Non-Allergic Asthma It is important to note that a significant proportion of asthma patients, perhaps almost half, present with a non-allergic form of the disease. This is also referred to as intrinsic asthma. These patients differ from allergic asthmatics in a few interesting and important ways: Allergic Non-Allergic Childhood onset Adult onset Family historyNo family history Symptoms induced by allergensSymptoms induced by stress, cold, exercise Elevated IgENormal or reduced IgE Significant Lung remodeling Little remodeling Eosinophil influxNeutrophil influx Steroid responsiveLess steroid responsive
Mast cell Resident cell in many tissues Best known for the causative agent in allergic disease Inflammatory mediators released – 1.Granule-associated mediators – Histamine, Serotonin, proteases 2.Eicosanoids - Prostaglandin D2, Leukotriene C4 3.Cytokines and chemokines– IL-2, IL-13, IL-6, MCP-1, TNF α, CXCL-8