Immunology LYMPHOID STRUCTURES

Immunology
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“I hate to disappoint you, but my rubber lips are immune to your charms.” ––Batman & Robin
“No State shall abridge the privileges or immunities of its citizens.” ––The United States Constitution
Immunology can be confusing and complicated, but luckily the USMLE tests only basic principles and facts in this area. Cell surface markers are important to know because they are clinically useful (for example, in identifying specific types of immune deficiency or can- cer) and are functionally critical to the jobs immune cells carry out. By spending a little extra effort here, it is possible to turn a tradition- ally difficult subject into one that is high yield.
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IMMUNOLOGY—HIGH-YIELD CLINICAL VIGNETTES

Patient with Mycoplasma What types of IgM. pneumoniae exhibits immunoglobulins are cryoagglutinins during recovery reacting? phase.
Young child presents with tetany What immune cell is T cell (DiGeorge). and candidiasis. Hypocalcemia deficient? and immunosuppression are found.
Young child has recurrent lung What enzyme is deficient NADPH oxidase (chronic infections and granulomatous in neutrophils? granulomatous disease). lesions.
Patient presents with recurrent What complement C6–C8. Neisseria infections. proteins are deficient?
Woman complains of a malar The presence of which Anti-dsDNA and anti-Smith. rash and arthritis. antibodies are specific for SLE?
Patient presents with dermatitis, What disease process is Graft-versus-host disease. enteritis, and hepatitis after bone occurring? marrow transplantation.
IMMUNOLOGYHIGH-YIELD PRINCIPLES
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IMMUNOLOGY—LYMPHOID STRUCTURES
Lymph node A 2° lymphoid organ that has many afferents, 1 or more efferents. Encapsulated, with trabeculae. Functions are nonspecific filtration by macrophages, storage and activation of B and T cells, antibody production. Follicle Site of B-cell localization and proliferation. In outer cortex. 1° follicles are dense and dormant. 2° follicles have pale central germinal centers and are active. Medulla Consists of medullary cords (closely packed lymphocytes and plasma cells) and medullary sinuses. Medullary sinuses communicate with efferent lymphatics and contain reticular cells and macrophages. Paracortex Houses T cells. Region of cortex between Paracortex enlarges in an follicles and medulla. Contains high endothelial extreme cellular immune venules through which T and B cells enter from response (i.e., viral). blood. In an extreme cellular immune response, paracortex becomes greatly enlarged. Not well developed in patients with DiGeorge syndrome.
Lymph drainage Area of body 1º lymph node drainage site 1. Upper limb, 1. Axillary lateral breast 2. Stomach 2. Celiac 3. Duodenum, 3. Superior mesenteric jejunum 4. Sigmoid colon 4. Colic →inferior mesenteric 5. Rectum (lower 5. Internal iliac part), anal canal above pectinate line 6. Anal canal below 6. Superficial inguinal pectinate line 7. Testes 7. Superficial and deep plexuses →para-aortic 8. Scrotum 8. Superficial inguinal 9. Thigh (superficial) 9. Superficial inguinal 10. Lateral side of 10. Popliteal dorsum of foot
Right lymphatic duct––drains right arm and Thoracic duct––drains right half of head. everything else.