Lymphoid System Dr. Raid Jastania Dec, 2006

By the end of this session you should be able to: –Describe the components of the lymphoid system –List the disorders of the lymphoid system –List the causes of leukopenia and leukocytosis –Be able to process a lymph node biopsy –Understand and pathology of common infections involving lymph nodes

Contents Introduction Processing lymph node biopsy Leukopenia and Leukocytosis Infectious mononucleosis Acute and chronic lymphadinitis Cat-scratch disease Granulomatous inflammation

Basics What is the lymphoid system? –Components, function

Basics What is the lymphoid system? –Components, function Consists of the lymph with the lymphatic channels and vessels, lymph nodes, thymus, spleen, and the visceral lymphoid tissue (GI, respiratory tract etc.) Function: Immune system.

Basics What are the types of lymphocytes?

Types of lymphocytes T cell: –Cellular immunity –Produced in the bone marrow, mature in the thymus and released in the peripheral circulation –2 subsets: T helper, and T cytotoxic –Th1, Th2

Types of lymphocytes B cells: –Humoral immunity (antibody production) – Produced in the bone marrow, released to the lymphoid organs. When activated matures to form plasma cells

Types of lymphocytes What is the effect of T cells on B cells?

Basics What are the disorders of the lymphoid system?

List of Causes (or Disorders) Primary vs Secondary Congenital/Genetic vs Acquired The Acquired: Non-neoplastic, Neoplastic Non-neoplastic: Inflammatory, Idiopathic Inflammatory: Infection, Drugs, Toxins, Metabolic, Immune –Eg. Causes of hepatitis, heart failure, lymphadenopathy

Basics Symptoms and signs of lymphoid disorders.

Symptoms and Signs Primary, Secondary, Non specific Anatomical and Functional Complications of the disease process –Eg. Features of lymphoma Lymphadenopathy, fever, night sweat, wt. Loss Mass effect, vascular obstruction, eg. Superior vena cava syndorme. Suppressed immunity. –Eg. Features of chronic liver disease.

Basics Clinical information needed –History, Examination, investigations.

Basics Lymph Node Biopsy

Basics Normal lymph node

Anatomy of the Lymph Node 3 major zones: –Cortex: B-cells, Follicles, Mantle cells, Marginal zones, secondary follicles, germinal centers –Paracortex: T-cells, interdigitating dendritic cells, post capillary venules –Medulla: Lymph sinuses, veins, arteries, plasma cells, B-cells mainly

Cells in the Lymph Node T-cells: –Bone marrow---Thymus---Paracortical area of LN –Cellular immunity B-cells: –Bone marrow, gut lymphoid tissue –Cortex and Medulla of LN –Humoral immunity Natural Killer cells –Do not mark as B or T –No specific distribution Others: Histiocytes, follicular and interdigitation dedritic cells, plasma cells, neutrophils, endothelial cells

Flow cytometry

Case 50 year old man with Diffuse large B cell lymphoma. He received 4 cycles of chemotherapy. Now he has neutropenia.

List of Causes Primary vs Secondary Congenital/Genetic vs Acquired The Acquired: Non-neoplastic, Neoplastic Non-neoplastic: Inflammatory, Idiopathic Inflammatory: Infection, Drugs, Toxins, Metabolic, Immune –Eg. Causes of hepatitis, heart failure, lymphadenopathy

Non-Neoplastic disorders Leukopenia –Any type of the white blood cell –Causes: congenital, acquired –Neutropenia

Non-Neoplastic disorders Leukopenia –Any type of the white blood cell –Causes: congenital, acquired –Neutropenia Inadequate or ineffective hematopoiesis Destruction of neutrophils Clinical presentation: malaise, fever, infections, oral ulcers

Reactive Leukocytosis Neutrophilic leukocytosis Lymphocytosis Eosinophilic leukocytosis Basophilic leukocytosis Monocytosis

Case 21 year old female with history of bilateral cercical lymphadenopathy for 2 months. The illness started with sore throat and few days of fever.

List of Causes Primary vs Secondary Congenital/Genetic vs Acquired The Acquired: Non-neoplastic, Neoplastic Non-neoplastic: Inflammatory, Idiopathic Inflammatory: Infection, Drugs, Toxins, Metabolic, Immune –Eg. Causes of hepatitis, heart failure, lymphadenopathy

Infectious Mononucleosis EBV infection Acute self-limiting Adolescents and young adults 1.Fever, sore throat, generalized lymphadenopathy 2.Lymphocytosis with atypical lymphocytes on smear 3.Positive serology for EBV

Infectious Mononucleosis Route of infection: saliva? Types of infection: Productive, latent Polyclonal B cell proliferation Morphology: –Peripheral blood, Lymph nodes, Spleen, Liver EBV in immunosuppresed individual EBV in X-linked lymphoproliferative syndorme

Case 10 year-old boy with right axillary lymphadenopathy for 2 weeks He had forearm injury with skin infection.

List of Causes Primary vs Secondary Congenital/Genetic vs Acquired The Acquired: Non-neoplastic, Neoplastic Non-neoplastic: Inflammatory, Idiopathic Inflammatory: Infection, Drugs, Toxins, Metabolic, Immune –Eg. Causes of hepatitis, heart failure, lymphadenopathy

Case 50 year old lady with Rheumatoid arthritis for several years She has generalized lymphadenopathy.

List of Causes Primary vs Secondary Congenital/Genetic vs Acquired The Acquired: Non-neoplastic, Neoplastic Non-neoplastic: Inflammatory, Idiopathic Inflammatory: Infection, Drugs, Toxins, Metabolic, Immune –Eg. Causes of hepatitis, heart failure, lymphadenopathy

Reactive lymphadenitis Acute non-specific lymphadenitis –infections –Local or generalized –Morphology Chronic non-specific lymphadenitis –Follicular hyperplasia –Paracortical lymphoid hyperplasia –Siuns histiocytosis

Case 15 year old boy with right cervical lymphadenopathy for 6 weeks No previous history of illness Lymph node biopsy shows necrotizing lymphadenitis

List of Causes Primary vs Secondary Congenital/Genetic vs Acquired The Acquired: Non-neoplastic, Neoplastic Non-neoplastic: Inflammatory, Idiopathic Inflammatory: Infection, Drugs, Toxins, Metabolic, Immune –Eg. Causes of hepatitis, heart failure, lymphadenopathy

Cat-Scratch Disease Infection: Bartonella henselae Acute self-limiting Children Regional lymphadenopathy: axilla, neck Regress over 2-4 months Morphology

Case 28 year old Indian male. Has generalized lymphadenopathy, more prominent in the neck bilaterally. Lymph node biopsy shows granulomatous inflammation

List of Causes Primary vs Secondary Congenital/Genetic vs Acquired The Acquired: Non-neoplastic, Neoplastic Non-neoplastic: Inflammatory, Idiopathic Inflammatory: Infection, Drugs, Toxins, Metabolic, Immune –Eg. Causes of hepatitis, heart failure, lymphadenopathy

Granulomatous inflammation Types: necrotizing, non-necrotizing Causes: infectious, non- infectious Infections: bacterial (T.B), fungal (Histoplasma), Parasitic (Schistosoma), Viral (less likely) Non-infectious: Foreign body, immune (sarcoidosis), idiopathic

By the end of this session you should be able to: –Describe the components of the lymphoid system –List the disorders of the lymphoid system –List the causes of leukopenia and leukocytosis –Be able to process a lymph node biopsy –Understand and pathology of common infections involving lymph nodes