Blood Overview

Overview of Blood Cells and Immunity

  • White Blood Cells (WBCs): Also known as leukocytes, they protect against infection.

  • Production: WBCs are produced in the bone marrow.

Types of Immunity

  • Innate Immunity:

    • First line of defense against pathogens.

    • Includes neutrophils and macrophages.

    • Involves inflammatory responses.

  • Adaptive Immunity:

    • Specific and acquired immunity.

    • Involves B and T lymphocytes.

    • Includes memory cells that help in quicker responses upon re-exposure to pathogens.

Epidemiology

  • Leukemia:

    • Characterized by the proliferation of cancerous WBCs.

  • Lymphomas:

    • Alterations in leukocyte function.

Quantitative Alterations of Leukocytes

  • Leukocytosis:

    • Higher than normal WBC counts.

    • May be a normal protective response to stressors or infections or can be pathological.

  • Leukopenia:

    • Lower than normal WBC counts.

    • Always abnormal and predisposes individuals to infections.

Basic Concepts of WBC Function

  • Categories of WBCs:

    • Monocytes:

    • Mature into macrophages and are involved in phagocytosis and cytokine synthesis.

    • Lymphocytes:

    • T and B cells that provide long-term immunity.

    • B cells specifically produce antibodies (immunoglobulins, Igs).

    • Granulocytes:

    • Subdivided into basophils, eosinophils, and neutrophils.

    • Neutrophils are the most common granulocyte and are also known as polymorphonuclear (PMN) cells.

Structure of the Lymphatic System

  • Components include:

    • Tonsils

    • Cervical lymph nodes

    • Axillary and inguinal lymph nodes

    • Thymus gland

    • Peyer's patches in the intestinal wall

    • Spleen

    • Right lymphatic duct and thoracic duct

    • Red bone marrow

Types and Functions of Agranulocytes

  • Monocytes:

    • Make up 2%–10% of circulating WBCs.

    • Phagocytose pathogens and synthesize cytokines.

    • Dendritic Cells:

    • Act as antigen-presenting cells.

  • Lymphocytes:

    • Comprise 20%–40% of circulating WBCs.

    • Provide long-term immunity through T and B cells.

    • B Cells:

    • Produce antibodies.

Macrophage Function and Phagocytosis

  1. Movement: Macrophages can exit capillaries to engulf antigens.

  2. Engulfment: They capture the bacteria (antigen).

  3. Digestion: Lysosomes containing enzymes digest the antigens.

Granulocytes Overview

  • Cytoplasm contains granules filled with chemicals.

  • Includes three types:

    • Neutrophils: Most common; indicate infection (known as “Segs” for mature & “Bands” for immature).

    • Eosinophils: Involved in allergic reactions and parasitic infections.

    • Basophils: Release histamine in allergic responses.

Alterations in WBC Number

  • Types:

    • Leukocytosis: Increase in WBCs.

    • Leukemoid Reaction: Extreme leukocytosis.

    • Leukopenia: Decrease in WBCs, leading to increased infection risk.

    • Neutrophilia: Increased neutrophils, typical in early infection or inflammation.

    • Neutropenia: Reduced neutrophils from various causes.

Eosinophilia and Eosinopenia

  • Eosinophilia: Increased eosinophils due to hypersensitivity reactions, often linked to allergic responses.

  • Eosinopenia: Reduced eosinophils, clinical importance less documented.

Special Functions of Neutrophils

  • Mature Neutrophils: Known as “Segs”;

  • “Bands”: Immature neutrophils; a high number signifies an increased demand for neutrophils, termed a shift-to-the-left.

Basophils Overview

  • Basophilia: Increased basophils during inflammation or allergic responses.

  • Basopenia: Associated with acute infections or prolonged steroid therapy.

Monocytes and Their Alterations

  • Monocytosis: Increased circulating monocytes, often seen with neutropenia during bacterial infections.

  • Monocytopenia: Decrease in monocytes; less understood.

Lymphocyte Changes

  • Lymphocytosis: Increased lymphocytes, common in viral infections such as Epstein-Barr virus or leukemia.

  • Lymphocytopenia: Low lymphocyte levels, leading to immune concerns.

Lymphadenopathy

  • A condition of enlarged lymph nodes:

    • Local: Associated with nearby inflammatory lesions.

    • Generalized: Present in more widespread disease processes (malignant/non-malignant).

Overview of Red Blood Cells (RBC)

  • Erythrocytes (RBCs): Contain hemoglobin (Hgb), facilitating oxygen transport.

  • Key Disorders:

    • Polycythemia: Overproduction of RBCs, less common than anemia.

    • Anemia: Deficiencies in RBC quantity or quality.

Erythropoiesis and Blood Formation

  • Process of RBC maturation from pluripotent stem cells in bone marrow, with reticulocytes being immature RBCs that are vital for assessing RBC production.

Breakdown of Red Blood Cells

  • Components of Hemoglobin:

    • Comprised of heme (iron, biliverdin, bilirubin) and globin portions.

Iron Metabolism Related to RBC Formation

  • Importance of Iron: Essential for Hgb production.

  • Transferrin: Transports iron;

  • Total Iron Binding Capacity (TIBC): Elevated when iron levels are low, indicating increased binding capacity.

  • Ferritin: Major iron storage complex, primarily in bone marrow, liver, and spleen.

Blood Typing and Antibodies

  • Agglutinogens: Antigens on RBC surfaces, classified into types A and B leading to AB and O blood types.

  • Rh Factor: Presence or absence of D antigen denoting Rh positive or negative blood types (e.g., A+, AB-, etc.).

  • Transfusion Risks: Recipients develop antibodies against non-self antigens, leading to potential transfusion reactions. Type A blood has anti-B antibodies; type O is a universal donor while type AB is a universal recipient.

Assessment of RBCs

  • Hemoglobin (Hgb):

    • Normal levels: Males 13 to 18 g/dL, Females 12 to 16 g/dL.

  • Hematocrit (Hct):

    • Normal percentages: Males 45%–52%, Females 37%–48%.

  • Total RBC count:

    • Males 4.5 to 5.5 million/mm³; Females 4.0 to 4.9 million/mm³.

Evaluation Metrics for RBCs

  • Reticulocytes:

    • Immature RBCs, typically 1% of total RBCs.

  • Mean Corpuscular Volume (MCV):

    • Indicates size; classified as macrocytic, normocytic, microcytic.

  • Mean Corpuscular Hemoglobin (MCH):

    • Indicates color; normal range is 27–32 picograms to describe chromic states (hyperchromic, normochromic, hypochromic).

  • Mean Corpuscular Hemoglobin Concentration (MCHC): Concentration of hemoglobin per volume of RBCs (gm/dL).

  • Red Cell Distribution Width (RDW): Variability in RBC size.

Overview of Anemia

  • Definition: Reduction in RBCs either by quantity or quality of hemoglobin.

  • Causes:

    • Impaired production, increased destruction, or blood loss (acute/chronic).

Classification of Anemias

  • Etiologic Classifications (causes):

    • Size: Identified by terms ending in “-cytic”.

    • Hemoglobin content: Identified by terms ending in “-chromic” (e.g., microcytic, hypochromic).

  • Microcytic Hypochromic: Disorders impacting hemoglobin synthesis (e.g., iron deficiency anemia).

  • Macrocytic: Disorders due to maturation issues in erythroid precursors.

  • Normocytic-normochromic: RBCC shape indicates causative factors of the anemia.

Different Types of Anemias

  • Aplastic Anemia: Associated with malfunction in bone marrow.

  • Hypochromic Anemia: Often linked to iron or vitamin deficiency.

  • Pernicious Anemia: Lack of intrinsic factor causing vitamin B12 absorption issues.

  • Genetic Anemias: Conditions such as Sickle Cell Anemia and hereditary types.

Size of RBCs and Related Conditions

  • MCV Range: 82-99 μm³; various conditions impact size and hemoglobin levels.

Symptoms of Anemia

  • Common symptoms include fatigue, increased heart rate, shortness of breath, headaches, dizziness, and chest pain.

Hemolytic Anemias

  • Conditions where destruction of erythrocytes exceeds production.

  • Causes include:

    • Hemoglobinopathies, autoimmune disorders, transfusion reactions.

Sickle Cell Anemia

  • An autosomal hemoglobinopathy, severe homozygous form; increases vulnerability to malaria.

  • Characteristics: Misshaped (sickle) RBCs, lifespan reduced, risk of vaso-occlusive crises particularly under stress.

Thalassemia Overview

  • Genetic defect leads to abnormal polypeptide chains in hemoglobin, categorized into major and minor forms.

Blood Transfusion Reactions

  • Reactions include hemolytic transfusion reactions; necessitate double-checking blood types to ensure compatibility.

Lead Poisoning Anemia

  • Lead disrupts hemoglobin synthesis, triggers hemolysis; important consideration in pediatrics.

Megaloblastic Anemias

  • Characterized by unusually large RBCs due to defective DNA synthesis (common deficiency in vitamin B12 and folate).

Conditions Related to Megaloblastic Anemias

  • Pernicious Anemia: Lack of intrinsic factor; can be autoimmune.

  • Folate Deficiency: Necessary for RNA and DNA synthesis; absorption occurs at the upper small intestine.

Microcytic-Hypochromic Anemia Overview

  • Characterized by small RBCs with less hemoglobin; caused by iron metabolism disorders.

Clinical Manifestations of Anemia of Chronic Disease

  • Mild to moderate anemia due to chronic illness; impaired erythropoiesis and iron metabolism issues.

Aplastic Anemia

  • Pancytopenia, often autoimmune; evaluation involves bone marrow biopsy.

Myeloproliferative Disorders

  • Polycythemia Vera: Non-malignant condition causing RBC, WBC, and platelet overproduction.

  • Primary vs. Secondary Polycythemia: Differentiated by cause; significant implications for treatment.

Hemostasis Overview

  • Hemostasis: Represents the process of stopping bleeding; involves primary (platelet aggregation) and secondary (fibrin clot formation) responses.

Coagulation Factors

  • Coagulation factors participate in a cascade reaction; calcium and vitamin K are vital.

  • Pathways include intrinsic and extrinsic, converging at common points leading to clot formation.

Clot Dissolution

  • Fibrinolysis is essential; involves tissue plasminogen activator (tPA) converting plasminogen to plasmin to break down clots.

Thromboembolic Disease Overview

  • Refers to blockage in vessels by thrombi or emboli, leading to tissue death from oxygen deprivation.

Disorders of Platelets

  • Thrombocytopenia: Low platelet count, resulting in varying degrees of bleeding risk.

Conditions Affecting Platelet Function

  • Include immune-mediated disorders like ITP and TTP, each with distinctive pathophysiology and manifestations.