Intermediate immunology

A family of proteins
Synthesised in liver
Can be activated direct in the innate system or by antibody binding (in the adaptive system)
Involves an activation cascade (similar to clotting cascade)
Functions including tagging (opsonisation) for destruction or direct membrane disruption

Y-shaped Protein molecule
Part of adaptive response to recognise specific antigens
Similar basic structure but wide genetic variations
IgG (gammaglobulin) is the main form in circulation
Each molecule is unique and specific to an epitope (each antigen may have several epitopes)
Ig that act against self-antigens are normally selected out or the response suppressed or diminished (see immuno tolerance)
Synthesised by B cells (cf other globulins made by liver)
Secreted (plasma B cells) or attached to surface (memory B cells)
Each B cells is associated with a unique Ig
B cells can be cloned (identical copies made) when required (adaptive immunity, memory)
Unique antibody fits to unique antigen like lock-and-key
After initial response, subsequent antibody responses to specific pathogen will be more vigorous.
Ig may exist as isotypes (polymeric versions/multiples) and found in different parts of the body with slightly different responses when activated e.g. IgE, IgA, IgM
Structure composed of two heavy chains and two light chains
Two ends of the 'Y' = Fc region (bind to the antigen)
Stem of the 'Y' = Fab region (bind to immune cell or complement)

Myeloid line (innate immunity) - granulocytes, mast cells (also RBCs and megakaryocytes>platelets)
Granulocytes - Neutrophils, Basophils, Eosinophils
Lymphoid line (adaptive immunity) - Natural killer cells, Lymphocytes
Lymphocytes - T cells, B cells>Plasma cells

+ Dendritic (Langerhans) cells - derived from both myeloid and lymphoid lines

Major component of adaptive humoural immunity
Produced in bone marrow but enter circulation and reside in lymph tissue
Antigen recognition occurs on B cell surface antibody
Internalisation of Ag-Ab complex is then presented onto cell surface for activation of T cells

Major component of adaptive cell-mediated immunity
Produced in thymus early in life but then reside in lymph tissue
Antigen recognition only in conjunction with intracellularly processed material 'presented' on host cell surfaces
T helper cell recognises antigens from APCs (with MHC II) and cytotoxic T cell recognises antigens from host cells (with MHC I)
T helper cell engages phagocytes, matures B cells and release cytokines
Cytotoxic T cell kills infected cells

Cells that internalise foreign material, processed it and then 'presents' on its surface to be recognised by specific T cells
Antigen is presented in combination with Major histocompatibility complex molecules
MHC I found on most host cells, MHC II found on immune cells
Examples - dendritic cells, macrophages, B cells
Two types - professional (presents antigen without co-stimuli) and non-professional (presents antigen only in presence with certain stimuli)
B cells re-present processed antigen with MHC II receptr by internalling Ab-Ag complex from its surface

The process by which antigens are presented or circulated so that the immune system can continously monitor self or non-self and eliminate non-self agents
Involves antigen presenting cells, the major histocompatibility complex, lymphatic system

The process by which 'self' is protected from attack by the immune system
Central tolerance - B & T cells are deleted before development (occurs esp in fetus but also in adult life)
Peripheral tolerance - various mechanisms, regulatory T cell suppression, immunoprivilege

Areas of the body where there is usually no immunosurveilliance ('immune to immune system' e.g. testis, placenta, eyes)
May be subject to attack if the immunological barriers are breached
e.g. testis-blood barrier is disrupted in one testis, antigenic sites are exposed and will activate the immune system. Sperm in the other testis then becomes vulnerable to immune attack resulting in infertility. A similar condition happens in eye trauma.