A. Incorrect! The duodenum drains to the superior mesenteric lymph nodes. B. Incorrect! The jejunum drains to the superior mesenteric lymph nodes.

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1 USMLE Step 1 Problem Drill 11: Immunology Question No. 1 of A 67 year old man is discovered to have metastatic disease involving his inferior mesenteric lymph nodes. His primary cancer is most likely from which of the following origins? Question #01 (A) Duodenum (B) Jejunum (C) Sigmoid colon (D) Lower rectum (E) Anus The duodenum drains to the superior mesenteric lymph nodes. The jejunum drains to the superior mesenteric lymph nodes. C. Correct! The sigmoid colon drains to the colic and then to the inferior mesenteric lymph nodes. D. Incorrect! The lower rectum and anal canal above the pectinate line drain to the internal iliac lymph nodes. The anus, which is below the pectinate line drains to the superficial inguinal lymph nodes. It is important to note that lymph drainage for specific gastrointestinal structures flows to certain primary lymph node sites, the: Stomach drains to the celiac lymph nodes. Duodenum and jejunum drain to the superior mesenteric lymph nodes. Sigmoid colon drains to the colic and then to the inferior mesenteric lymph nodes. Lower rectum and anal canal above the pectinate line drain to the internal iliac lymph nodes. Anal canal below the pectinate line drains to the superficial inguinal lymph nodes. (C)Sigmoid colon RapidLearningCenter.com Rapid Learning Inc. All Rights Reserved

2 Question No. 2 of T cell differentiation into CD4 and CD8 cells takes place in which of the following lymphoid system structures? Question #02 (A) Lymph nodes (B) Lymphatic channels (C) Bone marrow (D) Thymus gland (E) Spleen By the time that T cells reach the lymph nodes in the course of their differentiation, they have already differentiated into CD4 and CD8 cells in the thymus. They do further differentiate in the lymph nodes as follows: CD4 to T H 1 and T H 2 cells and CD8 to cytotoxic T cells. T cell differentiation does not occur in the lymphatic channels. Bone marrow houses T cell precursors, which do not begin to differentiate until they reach the thymus gland. D. Correct! T cell differentiation from T cell precursors into CD4 and CD8 cells takes place in the thymus gland. The spleen houses T cells, but does not contribute as a site of their differentiation process. T cell precursors from the bone marrow travel to the thymus where they differentiate into CD8+ cells and CD4+ cells. These cells then travel to the lymph nodes were they further differentiate with the: CD8+ cell differentiating to a cytotoxic T cell. CD4+ cell differentiating to a helper T cell, which differentiates further into T H 1 and T H 2 cells. RapidLearningCenter.com Rapid Learning Inc. All Rights Reserved

3 Question No. 3 of Which of the following is a required component for Tc cell activation? Question #03 (A) MCH II (B) T H cell IL-2 (C) IgD (D) B7 (E) CD28 MCH II is a component in T H cell activation. B. Correct! T H cell IL-2 is a required component for Tc cell activation. IgD is found in serum and on B cell surface; its function is unknown. D. Incorrect! B7 is a component in T H cell activation. CD28 is a component in T H cell activation. For T H cell activation, a foreign body undergoes phagocytosis by an APC, then: Signal 1 occurs when the foreign antigen now present on MHC II of the APC is identified by TCR on the T H cell, and Signal 2 is a costimulatory signal as B7 and CD28 interact. For Tc cell activation: Signal 1 occurs when endogenously synthesized proteins are presented on MHC I of the virus infected cell and identified by TCR on the Tc cell, and Signal 2 occurs when the T H cell IL-2 activates the Tc cell to destroy the virus infected cell. RapidLearningCenter.com Rapid Learning Inc. All Rights Reserved

4 Question No. 4 of Antibodies have roles in all of the following functions except for: Question #04 (A) Passive immunity (B) Opsonization (C) Active immunity (D) Complement activation (E) Cell mediated immunity Passive immunity refers to the therapeutic administration of antigen-specific antibodies after exposure to the antigen. Opsonization refers to an antibody promoting phagocytosis. Active immunity refers to the generation of antibodies after initial exposure to an antigen. D. Incorrect! Antibodies do function to activate complement. E. Correct! Antibodies do not play a role in cell mediated immunity, which refers to T cell response. There are 2 basic types of immunity: Active immunity occurs after exposure to foreign antigens. It has a slow onset and a long lasting result, lasting years or having memory. An example of active immunity would be the immune response to the measles, mumps and rubella vaccine (MMR) given to children. Passive immunity occurs after being given preformed antibodies from another host. This has a rapid onset and the effects are only temporary, lasting about 3 weeks. An example of passive immunity would be gammaglobulin given after hepatitis B exposure as a therapeutic measure. Antibody function: Opsonization the antibody promotes phagocytosis. Neutralization the antibody inhibits bacterial adherence. Compelement activation which promotes opsonization. (E)Cell mediated immunity RapidLearningCenter.com Rapid Learning Inc. All Rights Reserved

5 Question No. 5 of Which of the following immunoglobulin isotypes is found in secretions, where it prevents attachment of bacteria and viruses to mucous membranes? Question #05 (A) IgA (B) IgD (C) IgE (D) IgG (E) IgM A. Correct! IgA is found in secretions, where it prevents attachment of bacteria and viruses to mucous membranes. IgD is found in serum and on B cell surface; its function is unknown. IgE is the least abundant antibody and is responsible for immediate hypersensitivity by causing release of mediators from mast cells and basophils after exposure to an allergen. D. Incorrect! IgG is the most abundant antibody, a significant player in secondary response, fixes complement, opsonizes bacteria, neutralizes viruses and bacteria toxins, and crosses the placenta. IgM is generated in the primary response to an antigen, fixes complement, and does not cross the placenta. Immunoglobulin isotypes: IgG most abundant antibody, significant player in secondary response, fixes complement, opsonizes bacteria, neutralizes viruses and bacteria toxins, and crosses the placenta. IgA found in secretions, it prevents attachment of bacteria and virus to mucous membranes. IgM generated in the primary response to an antigen, fixes complement, does not cross the placenta. IgD found in serum and on B cell surface, function is unknown. IgE the least abundant antibody, responsible for immediate hypersensitivity by causing release of mediators from mast cells and basophils after exposure to an allergen. (A)IgA RapidLearningCenter.com Rapid Learning Inc. All Rights Reserved

6 Question No. 6 of Which of the following cytokines is secreted by T H 2 cells and encourages B cell differentiation? Question #06 (A) IL-1 (B) IL-2 (C) Il-4 (D) Il-5 (E) TNF IL-1 is secreted by macrophages and causes acute inflammation. IL-2 is secreted by T H cells and stimulates cytotoxic and helper T cell growth. IL-4 is secreted by T H 2 cells and encourages B cell growth. D. Correct! IL-5 is secreted by T H 2 cells and encourages B cell differentiation. TNF is secreted by macrophages and mediates septic shock. Cytokines refer to signalling molecules secreted by components of the immune system that facilitate cellular communication by carrying signals between cells and having an effect on them. There are a number of important cytokines secreted by different components of the immune system. For example: IL-1 secreted by macrophages and causes acute inflammation. IL-2 secreted by T H cells and stimulates cytotoxic and helper T cell growth. IL-4 secreted by T H 2 cells and encourages B cell growth. IL-5 secreted by T H 2 cells and encourages B cell differentiation. Gamma interferon secreted by Th1 cells and stimulates macrophages. TNF secreted by macrophages and mediates septic shock. (D)Il-5 RapidLearningCenter.com Rapid Learning Inc. All Rights Reserved

7 Question No. 7 of Which of the following types of hypersensitivity reactions occurs when antigenantibody complexes serve to activate complement which attracts neutrophils that release lysosomal enzymes? Question #07 (A) Hypersensitivity type I (B) Hypersensitivity type II (C) Hypersensitivity type III (D) Hypersensitivity type IV (E) All of the above Type I hypersensitivity reaction is antibody mediated with immediate reaction that is anaphylactic and atopic. Preformed IgE antibody present due to initial exposure to the antigen acts rapidly with subsequent antigen exposure to cause release of histamine from mast cells and basophils. Type II hypersensitivity reaction is antibody mediated where IgG and IgM attach to antigen on the pathogen to cause lysis by phagocytosis or complement activation. C. Correct! Type III hypersensitivity reaction occurs when antigen-antibody complexes serve to activate complement which attracts neutrophils that release lysosomal enzymes. D. Incorrect! Type IV hypersensitivity reaction is a delayed, cell mediated reaction in which sensitized T cells contact antigens and release lymphokines which lead to macrophage activation. C is the only correct answer. Hypersensitivity Type I: Type I hypersensitivity reaction is antibody mediated with immediate reaction that is anaphylactic and atopic. Preformed IgE antibody present due to initial exposure to the antigen acts rapidly with subsequent antigen exposure to cause release of histamine from mast cells and basophils. Hypersensitivity Type II: Type II hypersensitivity reaction is antibody mediated where IgG and IgM attach to antigen on the pathogen to cause lysis by phagocytosis or complement activation. Hypersensitivity Type III: Type III hypersensitivity reaction occurs when antigen-antibody complexes serve to activate complement which attracts neutrophils that release lysosomal enzymes. Hypersensitivity Type IV: Type IV hypersensitivity reaction is a delayed, cell mediated reaction in which sensitized T cells contact antigens and release lymphokines which lead to macrophage activation. (C)Hypersensitivity type III RapidLearningCenter.com Rapid Learning Inc. All Rights Reserved

8 Question No. 8 of Which of the following autoimmune diseases is the result of a type IV hypersensitivity reaction? Question #08 (A) Anaphylaxis (B) Hemolytic anemia (C) Rheumatiod arthritis (D) Graft-vs-host disease (E) All of the above Anaphylaxis occurs as the result of a type I hypersensitivity reaction. Hemolytic anemia occurs as the result of a type II hypersensitivity reaction. Rheumatiod arthritis occurs as the result of a type III hypersensitivity reaction. D. Correct! Graft-vs-host disease occurs as the result of a type IV hypersensitivity reaction, which is cell mediated. D is the only correct answer. Diseases caused by Type I hypersensitivity reaction include: anaphylaxis, penicillin allergy, and Allergic rhinitis or hay fever. Diseases cause by Type II hypersensitivity reaction include: hemolytic anemia, ITP, erythroblastosis fetalis, rheumatic fever, Grave s disease, and Myasthenia gravis. Diseases cause by Type III hypersensitivity reaction include: SLE, rheumatoid arthritis, polyarteritis nodosum, poststreptococcal glomerulonephritis, serum sickness, and arthus reaction. Diseases cause by Type IV hypersensitivity reaction include: type I diabetes mellitus, multiple sclerosis, Guillian-Barre syndrome, Hashimoto s thyroiditis, graft-vs-host disease, and Contact dermatitis. (D) Graft-vs-host disease RapidLearningCenter.com Rapid Learning Inc. All Rights Reserved

9 Question No. 9 of A child that presents with multiple staph aureus infections and chronic granulomatous disease has an immune deficiency that results from: Question #09 (A) Decreased production of B cells and T cells. (B) Decreased activation of B cells and T cells. (C) Decreased activation of macrophages. (D) A phagocytic cell deficiency. (E) An idiopathic cause. Immune deficiencies that result from decreased production of B cells and T cells are Bruton s agammaglobulinemia, DiGeorge syndrome (aka thymic aplasia), and severe combined immune deficiency (SCID). Immune deficiencies due to decreased activation of B cells, T cells or macrophages are Hyper IgM syndrome, Wiskott-Aldrich syndrome, IL-2 receptor deficiency, and Job s syndrome. Immune deficiencies due to decreased activation of B cells, T cells or macrophages are Hyper IgM syndrome, Wiskott-Aldrich syndrome, IL-2 receptor deficiency, and Job s syndrome. D. Correct! Chronic granulomatous disease is due to a phagocytosis deficiency of neutrophils due to lack of NADPH or similar enzyme activity. Children present with opportunistic bacterial infections, particularly S. aureus, E. coli and Aspergillus. Other diseases caused by this mechanism are Chediak-Higashi disease and Leukocyte adhesion deficiency syndrome type I. Immune deficiencies due to idiopathic B and T cell dysfunction are ataxia telangiectasia, selective immunoglobulin deficiency, common variable immunodeficiency, and chronic mucocutaneous candidiasis. Chronic granulomatous disease is due to a phagocytosis deficiency of neutrophils due to lack of NADPH or similar enzyme activity. Children present with opportunistic bacterial infections, particularly S. aureus, E. coli and Aspergillus. (D)A phagocytic cell deficiency. RapidLearningCenter.com Rapid Learning Inc. All Rights Reserved

10 Question No. 10 of A 49 year old woman presents with severe rheumatoid arthritis. Which of the following autoantibodies will be present at high levels in her serum? Question #10 (A) Antinuclear antibodies (ANA) (B) Anti-gliadin (C) Anti-basement membrane antibody (D) Anti-IgG (E) Anti-SS-A Antinuclear antibodies (ANA) are present in SLE. Anti-gliadin is present in celiac disease. Anti-basement membrane antibody is present in Goodpasture s syndrome. D. Correct! Anti-IgG is also referred to as rheumatoid factor and would be present in high levels in the serum of a patient with active rheumatoid arthritis. Anti-SS-A is present in Sjogren s syndrome. There are a number of autoantibodies known that are associated with specific autoimmune diseases. Some examples are: Antinuclear antibodies (ANA) present with SLE. Anti-IgG (rheumatoid factor) present with rheumatoid arthritis. Antigliadin present with celiac disease. Anti-basement membrane present with Goodpasture s syndrome. Anti-thyroglobulin and anti-microsomal present with Hashimoto s thyroiditis. Anti-SS-A and anti-ss-b present with Sjogren s syndrome. (D)Anti-IgG RapidLearningCenter.com Rapid Learning Inc. All Rights Reserved