Summary immunology Johns Hopkins - New 2024/2025 plus visuals and explanations

Complete summary Immunology

Johns Hopkins School of Medicine

Immunology 1 2024/2025




+ most important visuals included

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, Immunology
Introduction to the Immune System: Organs and Cells

Immunology - study of the immune system, protection of the body from invading
pathogens or foreign macromolecules (viruses, bacteria, protozoa, parasites, fungi).
Can protect against our own aberrant cells in tumour immunity. Can develop immune
responses against our own proteins in autoimmunity.

The Immune System - Recognises invading pathogens or foreign substances and defends
the body by producing an immune response. In many species, can be classified into sub-
systems: innate (non-specific) and adaptive (specific).

Pathogens - invading microoganisms that can cause disease. Eg. virus, fungi, bacteria,
protozoa, parasites.
Foreign substances include toxins and pollution.

How does the immune system recognise a pathogen?
 Invading pathogens have antigens (Ag) on their surface, which the
immune system recognises as non-self.
 Ag can be a cell surface protein, glycoprotein, liposaccharide, lipids.
 Non-specific innate immune cell receptors bind Ag directly.
 The presence of Ag causes immune response to be activated to destroy pathogen.

Innate immune cells - rapidly recognise pathogen Ags via invariant (non-specific)
receptors that trigger killing, pagocytosis and/or Ag presentation.

Adaptive immune cells - recognise pathogen Ags following presentation by APCs to
activate immune cell expansion followed by pathogen killing.

Immune System: Innate vs Adaptive


Innate Adaptive

Non-specific receptors Specific receptors
Responds quickly Responds slowly the 1st time
No memory Memory

, 1st Line of Defence - Mechanical/Chemical
Surface barriers protect against invading pathogens:
 Hair
 Keratin is the key structural material making up outer layer of skin
 Mucous membrane
 Antimicrobial secretions destroy pathogens before they enter the body

2nd Line of Defence - Innate Immunity

3rd Line of Defence - Adaptive Immunity



Organs of the Immune System
Specific organs required for development and function of the immune system
 Primary lymphoid organs - bone marrow and thymus, sites of immune cell origin
and lineage commitment
 Secondary lymphoid organs - lymph nodes, spleen and liver, trap antigens and
provide an environment for interaction with mature immune cells
 Tertiary lymphoid tissues - import immune cells and APC during an inflammatory
response, aggregates of cells in the lamina propria of:
MALT (mucosal associated lymph
tissue) GALT (gut associated lymph
tissue) BALT (bronchal associated
lymph tissue)
 All lymphoid organs connected by lymphatic system

Lymphatic System
 Lymph system similar to cardiac system, has one way flow (valves), begins in the
tissues and ends at the heart
 3 main parts: vessels carry fluid, lymph (fluid in vessels), lymph nodes
(filters lymph of pathogens)
 Plasma from blood vessels seeps into tissues
 Lymphatic vessels depend of muscle contraction for lymph flow back to heart
 Lymph and lymphocytes empty into the left subclavian vein of the heart

LYMPHOID PRIMARY ORGANS (Development)
Bone Marrow
 Site of haematopoiesis, formation of all blood cells from CD34+ HSC, B cell
receptor assembly
 BM MSC assist B cell maturation by:
1. Providing a source of self Ag → B cell apaptosis
2. Cytokine (IL-7) for B cell development

Haematopoiesis
 HSC (CD34+ Haematopoietic Stem Cell) - reside in bone marrow, pluripotent,
1/50000 BM cells, extremely proliferative if need arises
 HSC differentiate into common lymphoid or myeloid progenitor cells (lineage
commitment)
 Growth factors, cytokines determine cell lineage
 Mesenchymal stromal cells (MSC) support HSC development in BM and in vitro
 Haematopoietic Growth Factors - and cytokines determine cell lineage commitment:
o Myeloid Growth Factors
Multi-CSF (IL-3)
M-CSF (Macrophage
CSF) G-CSF
(Granulocyte CSF)