cardiff exam style questions Flashcards
define infection
invasion of an organism’s tissues by disease causing microorganisms, their multiplication and the reaction of host tissues to infectious agents
what is a pathogenic microorganism
microorganism that can enter the body and cause harm
define immunology
the branch of medicine and biology concerned with immunity.
what is immunity
protection against infectious diseases caused by microorganisms and cancer
what microorganisms cause infectious disease?
- protozoa
- fungi
- bacteria
- viruses
- parasites
what are the means of pathogen transmission
- airborne through respiratory tract
- oral-fecal route
- contaminated water
- blood transfusion and sharing of needles
categorize the immune system and its types
what is the immune function of the skin
- it acts as a barrier between the body and the external environment, preventing pathogen entry (stratum corneum)
- dendritic cells (Langerhans cells) present in the epidermis; they are responsible for the capture, processing, and presentation of antigens to T lymphocytes in local lymphoid organs. As a result, T lymphocytes express the cutaneous lymphocyte antigen (CLA) molecule, a modified form of P-selectin glycoprotein ligand-1.[1] Lymphocytes move to the epidermis where they reside as memory T cells, they will thus be activated and will trigger an inflammatory response.
what is the immune function of secretions e.g. tears/saliva
contain molecules that can neutralize bacteria
1- what is the thymus?
2- what is its function?
3- where is it located?
- encapsulated lymphoid organ where t cell maturation and differentiation occurs
- creates lymphocytes
- behind the sternum in the mediastinum
list the primary lymphoid tissues responsible for the proliferation of lymphocytes
- thymus
- bone marrow
- list the secondary lymphoid tissues
- what is the main function of the secondary lymphoid tissues
- lymph nodes/spleen/tonsils
- provide the environment for proliferation and maturation of adaptive immune cells (t/b) to filter and trap pathogens
what is a lymph node
encapsulated, trabeculated lymphoid organ that has many afferent and one or more efferent branches
what is the function of lymph nodes?
it functions as a filter, storage and active centre for t/b cells and antibody production
what are the 3 main components of the lymph nodes, and what are their roles
- follicle: b cell storage and proliferation
- medulla: has medullary cords and sinuses as filters
- paracortex: location of t cells
what are the anatomic structures of the spleen, and what are their roles
- sinusoids: elongated channels with fenestrated membranes and adjacent macrophages
- periarterial lymphatic sheath: red pulp that houses t cells
- follice: white pulp that houses b cells
what is the difference between adaptive and innate immunity?
adaptive: specific response to infectious agents that depend on antigen presentation, recognition and antibody response (memory/antibodies)
innate: physical and biochemical barriers inside and outside the body (no memory/no antibodies)
what organs are considered to be the first lines of defense?
- skin
- respiratory system
- gut
- genitourinary
- mucos/cilia/reflexes
true or false
elevation of body temperature is a first line of defense
true
what are the two main types of innate immune cells
- natural killer cells (cytolytic and cytotoxic granules)
- phagocytes (macrophages/neutrophils)
what is the difference between the two innate cells (natural killer and phagocytes)?
natural killer → recognize virally infected and malignant changes on the surfaces of cells and opsonized cells
phagocytes → engulf debris, destroy and remove them
what 3 main cells are capable of phagocytosis?
neutrophils
macrophages
dendritic cells
what is phagocytosis
recognition and ingestion of particles larger than 0.5 μm into a plasma membrane derived vesicle, known as phagosome
what is the function of mast cells and basophils
- secrete histamines (inflammatory mediators)
- responsible for allergic reactions (hypersensitivity type 1)
where do mast cells and basophils reside?
mast cells → tissues
basophils → blood
what is the function of phagocytes
- phagocytosis/neutralization
- respond to inflammation in tissues
how are phagocytes able to recognize microorganisms?
via pathogen associated molecular patterns on their surface and via pattern recognition receptors
briefly, what are the steps of phagocytosis
(i) recognition of the target particle,
(ii) signaling to activate the internalization machinery,
(iii) phagosome formation
(iv) phagolysosome maturation
what are the cell surface proteins of macrophages?
- MHC II
- B7
- CD40
- CD14
what is the main function of MHC II
present processed antigens, which are derived primarily from exogenous sources, to CD4(+) T-lymphocytes
why is MHC class II critical for the initiation of the antigen-specific immune response.
because they present processed antigens, which are derived primarily from exogenous sources, to CD4(+) T-lymphocytes
describe the mechanism of humoral innate response
defense mechanism that attacks pathogens in a rapid non-specific manner
what are examples of humoral innate response?
- fever
- complement
- inflammation
explain how fever occurs during infection
Exogenous pyrogens initiate fever by inducing host cells (primarily macrophages) to produce and release endogenous pyrogens such as interleukin-1
or
release of pyrogens increase body temperature via cyclooxegenase-2 (cox-2).
briefly explain the role of the complement system of humoral innate response
- plasma proteins, destroy cell membranes (lytic pore).
- Attract phagocytes & stimulate activity of other immune cells.(anaphylatoxins C3a, C5a).
- Promote phagocytosis (Opsonins, C3b/iC3b, C4b).
what causes an inflammation?
Mast cells release pro-inflammatory cytokines & chemokines causing blood vessels to dilate, allowing influx of immune cells and fluid (plasma). Symptoms are pain, swelling, redness and heat
what are the three methods by which the complement system is activated
classical → requires antibodies (IgM/IgG) to be bound to antigens
alternative → requires endotoxin or a foreign surface (bacterial surface)
lectin → requires bacterial carbohydrates
cell mediated adaptive immunity is activated upon ___________
humoral adaptive immunity is activated upon _______
direct contact with pathogen
antibodies
the adaptive immune response is said to be specific, what does that mean?
because of its ability to generate an immune memory, to clarify, repeated exposure to the same pathogen will produce an enhanced response to that same pathogen the next time it is exposed to
what are the main cells of the adaptive immune system
lymphocytes: T cells/ B cells
what is the function of t cells and b cells of the adaptive immune system
t cells → cell mediated activation of b cells and other immune cells (t helper/CD4+)/ direct killing (cytotoxic/CD8+)
b cells → make antibodies (IgM/IgG/IgA/IgE/IgD)
which cell structures allow adaptive specificity
b cell receptors
what does MHC stand for
major histocompatibility complex
where are the different classes of MHC expressed
MHC I → nucleated cell bodies
MHC II → on antigen presenting cells
what is the function of MHC
to bind peptide fragments derived from pathogens and display them on t cell receptors for recognition by the appropriate T cells
differentiate between cellular and humoral adaptive immune responses, providing appropriate examples
cellular
- targets cancer and infected body cells
- effected by cytotoxic t cells (CD8+)
humoral
- targets pathogens and antigens in blood/mucos
- t cells secrete cytokines to control activation of other cell type
what are the cell surface proteins expressed on each of the following immune cells
t-helper
cytotoxic t cells
t helper → CD4/TCR/CD3/CD28/CD40L
cytotoxic t cells → CD8/TCR/CD3
what is the function of cell surface proteins of T cells, provide an example
- recognizing fragments of antigen as peptides bound to major histocompatibility complex (MHC) molecules
- T helper bind and interact with b cells via CD40L on its surface and CD40 on the b cell
MHC is encoded by ________
human leukocyte antigen (HLA) genes
what are the HLA genes of MHC I/MHC II
MHC I → HLA-A/ HLA-B/HLA-C (on nucleated cells)
MHC II → HLA-DR/HLA-DP/HLA-DQ (antigen-presenting cells)
in the thymus, t cells differentiate into _____ & _____
CD4+ & CD8+
what do CD4+ cells differentiate into and what are their roles
they differentiate into T helper cells, which further differentiate into:
Th 1 → cellular adaptive response (Cytotoxic T cells, intracellular pathogens)
Th 2 → humoral adaptive response (B cells, extracellular pathogens)
Th 17 → extracellular bacteria and fungi, IL-17
T reg → control the immune response to self and foreign particles (antigens)
humoral adaptive immunity is dependent on ________& _______
antigens & antibodies