Lymphoid System

Dr. Raid JastaniaDec, 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 adults1. Fever, sore throat, generalized

lymphadenopathy2. Lymphocytosis with atypical lymphocytes

on smear3. 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