IMMUNOLOGY
By ZOHA and SAMIHA
Our learning objectives
pay attention – we will test you!
• Types of immune responses and cells involved
• Definitions :Learn them all but make sure you
understand affinity vs avidity
• CD markers, APCs… lots of letters but they will
make sense!
• Innate immunity – COMPLEMENT
• Antibodies
TYPES OF IMMUNITY
• INNATE immunity
1) Broad specificity
(require Pattern Recognition
Proteins)
2) Anatomical and
Physiological
barriers
3) Rapid response
4) NO immunological
memory
• ACQUIRED immunity
1) Antigen specific
2) Slower response
3) Involves
immunological
memory
** Innate immune system directs the acquired immune system
INNATE IMMUNE SYSTEM
THIS IS THE EARLY PHASE RESPONSE TO PATHOGEN
INVASION
CELLULAR COMPONENTS
HUMORAL COMPONENTS
NEUTROPHILS
CYTOKINES
NATURAL KILLER cells
COMPLEMENT
MONOCYTES/ MACROPHAGES
ANTI MICROBIAL Peptides
MAST cells
DENDRITIC cells
NB- some cellular and humoral factors of the innate system are also involved in
the adaptive system
The Key Players
NEUTROPHILS
(PMN):
•
Blood
Tissue via
DIAPEDESIS and
CHEMOTAXIS
• PHAGOCYTOSIS
This is aided by the process of
OPSONISATION
• KILLING
Oxygen dependent/independent
MACROPHAGES:
• Monocytes (blood)
Macrophages (tissue)
• Express pattern
recognition molecules
• Become activated by
molecular patterns on
bacterial surface
PHAGOCYTOSIS
CYTOKINE
RELEASE
WHAT HAPPENS IN SYSTEMIC INFECTION???
BACTERIAL SEPTIC SHOCK
COMPLEMENT SYSTEM
1)
ALTERNATIVE
PATHWAY
CLASSICAL
PATHWAY
2)
ANTIBODY
INDEPENDENT/
LECTIN PATHWAY
C3
3)
LEUKOCYTE
RECRUITMENT
MEMBRANE ATTACK
COMPLEXES
OPSONISATION
DEGRANULATION
OF MAST CELLS
LYSIS
** BUT THIS IS LIKE AN ENZYME CASCADE SYSTEM – small input gives BIG output
SO WE NEED TO CONTROL THIS SYSTEM
A TYPICAL LOCAL ACUTE
INFLAMMATORY RESPONSE
LOCAL ACUTE to SYSTEMIC ACUTE
PHASE response
• CYTOKINE INDUCED
FEVER
ACUTE PHASE
PROTEINS IN LIVER
1.
2.
3.
4.
LEUKOCYTOSIS
CRP
*Complement activation
by Lectin pathway
MBL
SERUM AMYLOID
COMPLEMENT
ADAPTIVE IMMUNE RESPONSE
THIS IS THE SPECIFIC, ANTIGEN MEDIATED
IMMUNITY
CELLULAR COMPONENTS
HUMORAL COMPONENTS
MONOCYTES/ MACROPHAGES
COMPLEMENT
DENDRITIC CELLS
CYTOKINES
MAST CELLS
ANTIBODIES
LYMPHOCYTES
LYMPHOCYTES
• PRODUCED IN THE PRIMARY LYMPHOID
ORGANS in HEMATOPOESIS
BONE MARROW
THYMUS
* So how does the body ensure that these naive lymphocytes interact with
complimentary antigens?
• INTERACTION WITH ANTIGEN OCCURS IN
SECONDARY LYMPHOID ORGANS
SPLEEN
LYMPH NODES
MALT eg Peyer’s
Patches
LYMPHOCYTES
B- Lymphocytes
•
•
•
•
Express CD19 and CD20
Express Surface Antigen
Receptor (Ig molecule).
Express MHC class II
molecules to “present”
antigens to T cells.
Produce antibodies to
mount an immune
response.
T- Lymphocytes
• All express CD3.
•2/3 express CD4 (helper T cells)
which secrete cytokines.
• 1/3 express CD8 (cytotoxic T cells)
which are responsible for lysing
infected cells and also producing
cytokines.
• Recognise processed antigen
presented by APCs with MHC class II.
APCs
•B cells (present to T cells)
•Dendritic cells (present to T cells)
• Follicular Dendritic cells (present to B cells)
• Activated Macrophages (present to T cells)
Antibodies
• Work by: Complement activation, opsonisation or cell
activation by antibody-binding receptors.
• Define Affinity: strength of an individual bond between an
antigen and an antibody
• Define Avidity: overall strength of all the bonds.
• This means IgM – which has more binding sites – will have a
greater avidity that IgG, which may have greater affinity.
• G – 4 subclasses. Most abundant. Placental transfer
• A – 2 subclasses. Secretory. Dimer
• M – agglutination in a primary response. Pentameric
molecule.
• E – parasites/allergies. Bound to mast cells &
basophils=histamine release.
• D – involved in B cell development.
MCQs
• ALL T cells express the CD3 marker
• Lysozyme is present in tears
• IgG antibodies are more efficient at
agglutination than IgM antibodies
• IgE is useful for passive immunity
• MALT is lymphoid tissue
• antibody-antigen complexes activate the
classical pathway of complement
• T
• T
• F
• F
• T
• T
Take home points
• This was just an overview of some areas – there
are lots of other details to remember that you
just need to get under your belt.
• Definitions – learn them basically but make sure
you understand first.
• Innate immunity – Complement – but you should
also look over acute phase response, learn the
proteins involved and try to integrate everything.
• Antibodies – we just gave you a way to remember
but you will need to learn the details.