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 ACQUIRED immunity 1) Antigen specific 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

MONOCYTES/ MACROPHAGES ANTI MICROBIAL Peptides 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): MACROPHAGES: PHAGOCYTOSIS KILLING Monocytes (blood) Macrophages (tissue) Express pattern recognition molecules Become activated by molecular patterns on bacterial surface NEUTROPHILS (PMN): Blood Tissue via DIAPEDESIS and CHEMOTAXIS PHAGOCYTOSIS This is aided by the process of OPSONISATION KILLING Oxygen dependent/independent CYTOKINE RELEASE PHAGOCYTOSIS

WHAT HAPPENS IN SYSTEMIC INFECTION??? BACTERIAL SEPTIC SHOCK

COMPLEMENT SYSTEM C3 MEMBRANE ATTACK COMPLEXES 1) 2) 3) ALTERNATIVE PATHWAY CLASSICAL PATHWAY ANTIBODY INDEPENDENT/ LECTIN PATHWAY 1) 2) C3 3) MEMBRANE ATTACK COMPLEXES LEUKOCYTE RECRUITMENT DEGRANULATION OF MAST CELLS OPSONISATION 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 LEUKOCYTOSIS FEVER ACUTE PHASE PROTEINS IN LIVER CRP MBL SERUM AMYLOID COMPLEMENT *Complement activation by Lectin pathway

ADAPTIVE IMMUNE RESPONSE THIS IS THE SPECIFIC, ANTIGEN MEDIATED IMMUNITY CELLULAR COMPONENTS HUMORAL COMPONENTS MONOCYTES/ MACROPHAGES COMPLEMENT DENDRITIC CELLS CYTOKINES MAST CELLS ANTIBODIES LYMPHOCYTES

MALT eg Peyer’s Patches 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 T- Lymphocytes B- 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. 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. 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 F 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

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.