Immunology Study Notes: Spring 2026
Immunology - Course Overview
Course Details
Course Title: Immunology
Course Code: 4465
Term: Spring 2026
Instructor: Dr. Natália Souza
Assignments and Readings
Achieve:
Homework and Adaptive Quiz for Chapters 1-3
Due: The Day Before the Exam
Reading:
Chapters 1-3
Tools:
Download iClicker app and link to your Achieve account
Concept Mapping Activity
Activity: Pair up and share individual concept maps
Focus on the following key concepts and their relationships:
Antigen
Immunity
Types of immunity:
Passive Immunity
Active Immunity
Characterized by:
Innate Immunity
Inflammatory Response
Pathogen Recognition
Adaptive Immunity
Humoral Immunity
Characterized by B lymphocytes (B cells)
First exposure to antigen leads to primary response
Second exposure leads to secondary response
Cell-mediated Immunity
Characterized by T lymphocytes (T cells)
Bind and recognize MHC with antigen
Stronger response through clonal selection
Major Themes in Immunology
Immune Dysfunction
Types of Immune Dysfunction:
Overactive or misdirected responses:
Hypersensitivity (e.g., allergies, asthma)
Autoimmunity (e.g., multiple sclerosis, Crohn's disease)
Immune Deficiency:
Primary (genetic) loss of function
Secondary (acquired) loss of function
Resulting in opportunistic infections (e.g., oral thrush caused by Candida albicans)
Immune Imbalance:
Uncontrolled inflammation
Proposed Role of the Microbiome
Commensal Microbes:
Humans harbor a diverse community of microbes, particularly in the gut
Gut-Brain Axis:
Intermediary role of the immune system
Influenced by dietary changes or stress leading to gut permeability issues
Dysbiosis:
Gut microbes leaking into the body provoke immune responses, potentially leading to
Immune overstimulation
Inflammation
Special Circumstances in Immunity
Tissue Transplants:
Body's natural response is to attack foreign tissue, necessitating intervention to avoid rejection
Cancer:
Cancer cells are typically tolerated by the immune system, making it difficult to generate effective immunity against them
Cells, Organs, and Microenvironments of the Immune System
Hematopoietic Stem Cells (HSCs)
Role in Immune Responses:
HSCs differentiate into various types of blood cells during hematopoiesis
All red and white blood cells arise from a pluripotent HSC
Hematopoiesis is a highly regulated process
Properties of HSCs
Key Properties:
Self-renewal capability
Differentiation potential into diverse cell types
Originating in fetal tissues, residing primarily in bone marrow of adults
Rarity: Less than 1 HSC per 50,000 bone marrow cells
Quiescence under homeostatic conditions
Transcription Factors in Hematopoiesis
Differentiation toward specific cell types reduces self-renewal ability and increases lineage commitment
Types of HSCs:
Long-term HSCs (LT-HSCs)
Short-term HSCs (ST-HSCs)
Multipotent progenitors (MPPs)
Common Myeloid and Lymphoid Progenitors
Hematopoiesis in Bone Marrow:
Continuous renewal and differentiation into:
Common Myeloid Progenitor (CMP) Cells:
Develops into various cell types including:
Red blood cells (erythrocytes)
Monocytes
Granulocytes (neutrophils, eosinophils, basophils)
Megakaryocytes (platelets)
Common Lymphoid Progenitor (CLP) Cells:
Develops into B lymphocytes, T lymphocytes, and innate lymphoid cells (ILCs)
Features of Cells in Human Blood
Cell Types, Counts, and Lifespans:
Cell Type
Cells/mm³
Total Leukocytes (%)
Life Span
Red blood cell
$5.0 imes 10^6$
N/A
120 days
Platelet
$2.5 imes 10^5$
N/A
5–10 days
Neutrophil
$3.7 – 5.1 imes 10^3$
50–70
6 hours to 2 days
Monocyte
$1 – 4.4 imes 10^2$
2–12
Days to months
Eosinophil
$1 – 2.2 imes 10^2$
1–3
5–12 days
Basophil
$<1.3 imes 10^2$
<1
Hours to days
Mast cell
$<1.3 imes 10^2$
<1
Hours to days
Lymphocytes
$1.5 – 3.0 imes 10^3$
20–40
Days to years
T lymphocytes
$0.54 – 1.79 imes 10^3$
7–24
B lymphocytes
$0.07 – 0.53 imes 10^3$
1–10
Total Leukocytes
$7.3 imes 10^3$
Distinguishing Blood Cells
Historical Classification:
Based on appearance using pH-sensitive stains:
Hematoxylin:
Basic, binds nucleic acids, stains blue
Eosin:
Acidic, binds proteins, stains pink
Antigen Presenting Cells
Functions of Macrophages and Monocytes:
Specialized for phagocytosis and antigen presentation to T cells via MHC molecules
Dendritic Cells:
Capture antigen, mature, migrate, and present to T cells, being the most potent antigen-presenting cells
B-Cell and T-Cell Development
B-Cell Development in Bone Marrow
Environment:
Develop in contact with stromal cells (e.g., fibroblasts, endothelial cells, macrophages)
Functions of Stromal Cells:
Facilitate HSC proliferation, direct migration, and stimulate differentiation
T-Cell Development in the Thymus
Maturation Process:
Begins in bone marrow and continues in the thymus, directing stages from double-negative to double-positive and then to single-positive cells
Positive and negative selection based on TCR affinity with MHC-peptides
Secondary Lymphoid Organs
Purpose:
Sites where lymphocytes encounter antigens, become activated, undergo clonal expansion, and differentiate
Types Include:
Lymph nodes
Spleen
Mucosa-associated lymphoid tissue (MALT)
Lymph Node Structure and Function
Architecture:
Distinct microenvironments for B-cells (cortex) and T-cells (paracortex)
Antigen entry via afferent vessels, naïve lymphocytes via High Endothelial Venules (HEV)
Functionality:
Activation interactions via fibroblastic reticular cell conduit (FRCCs)
Upon activation, B cells undergo clonal expansion and differentiation in germinal centers
The Spleen and Mucosa-Associated Lymphoid Tissue
Function of the Spleen:
First line of defense against blood-borne pathogens, filtering blood and housing red and white blood cells
Definition of MALT:
Defense mechanisms at mucosal surfaces, including specialized terms for different regions (e.g., BALT, NALT, GALT)
Tertiary Lymphoid Tissue
Developed at sites of immune activity/infection
Organized lymphoid microenvironments
Activated lymphocytes return to these sites as effector cells and may become memory cells.