INFECTION & IMMUNITY Flashcards
what causes infectious diseases?
bacteria & viruses
what are bacteria?
single cells with simple internal structure
what determines the strains bacteria take up?
cell wall structure either gram positive or gram negative
what are viruses and what are they made of?
infectious agents that can only replicate inside cells made of DNA or RNA contained in an envelope
what does a viruses envelope contain?
has proteins that enable virus to attach to cells & insert genetic material by combining with cell receptors
what is an opportunists pathogen?
microbes become important in some situations- fungi in patients undergoing chemo or long term antibiotic treatment due to debiliated state
what is the role of normal fungi in human?
support immunity, prevent overgrowth of pathogenic microbes, produce vitamin & other chemicals- can be affects by # of factors e.g. age, antibiotic use & diet
can normal flora be pathogenic?
yes- can contaminate surfaces or be transmitted person-to-person by direct contact or aerosols - can be removed by washing
what is person to person transmission occur from?
surgery, trauma, immune disease, treatment with immunosuppressive drugs
what are colonising microbes?
live on body for a period of days or months
what are the stages of infectious disease?
incubation period (no signs/symptoms present- patient usually infectious)- prodromal illness (person begins to feel ill)- acute illness (specific signs & symptoms appear)- recovery phase
what is a subclinical infection?
is an infection that, being subclinical, is nearly or completely asymptomatic
how do we prevent transmission of pathogens?
good hand hygiene, infectious patients can appear asymptomatic- additional precautions required for patient known or suspected of have an infection or have been colonised by potential pathogens
what are additional precautions?
sterilisation, disinfections which removes pathogens but not necessarily non-pathogenic organisms, or spores
what are the 3 broad components of immune system?
natural barriers, innate immunity (non-specific), acquired immunity (specific)
what are natural barriers?
skin, tears, secretions, flushing
what is innate immunity?
when first-line defences are breaches the non-specific inflammatory response occurs- macrophages release cytokines, which activate other cells of immune system and activate inflammatory response
what are the signs of inflammation?
redness (increased blood flow), pain (release of chemical that activate nociceptors), swelling (increased vascular permeability), heat (increased blood flow), loss of function- can be acute or chronic
what does an inflammatory response result in?
tissue damage- may be direct cause of disease, may contribute to pathogenesis of disease, may need to be suppressed in some disease (e.g.pneumonia)
what is acquired immunity?
it is directed against a specific antigen only, systemic not localised, should only occur in respose to foreign antigens, has memory
what are the 2 components of acquired immunity?
humoral immunity & cell mediated immunity
what is humoral immunity?
involves antibodies produced by B lymphocytes in response to antigens from bacteria, bacterial toxins or free viruses
what is the function of antibodies?
phagocytosis of antigen by neutrophils, precipitation, neutralization, lysis of antigenic cell membran, opsonisation (increasing susceptibility to phagocytosis)
what is cell medicated immunity?
response to virus infected cells, tumour cells & foreign tissue - antigens activate T cells
what are the types of T cells?
killer T cells destroy infected/foreign cells, helper T cells (stimulate & active other T cells, activate B cells), suppressor T cells make the immune response self limiting
what is active immunity?
body produces antibodies & develops memory against specifc antigens by production of memory cells- can be naturally acquired through contact with pathogen & artificially acquired through vaccination
what is passive immunity?
provides temporary protection- can be naturally acquired through maternal antibodies & artifically acquired through injected immunoglobulins
what are the cell types & molecules of innate immunity?
cell types (phagocytes, natural killer cells, mast cells, dendritic cells)- molecules (cytokines, complement, acute phase proteins)
what are cell types & molecules of acquired immunity?
cells (T & B cells)- molecules (antibodies & cytokines)
what are th einteractions between components of immune system?
cytokines produces by macrophages help induce the specific immune response- complement of the innate immune system ban be activated by antibodies
what is the function of the lymphatic system?
collects intersitial fluid into lymphatic capillaries- capillaries join to form collecting vessels which pass through lymoh nodes & return to the venous blood
where are cells of lymphatic system located?
in lymph nodes - approx. 600
what is lymphoedema?
accumulation of fluid in soft tissue as result of impaired lymphatic drainage- causes inflammation, adipose tissue hypertrophy & fibrosis
what can lymphoedema be due to?
primary hereditary or associated with congential conditions- secondary due to surgery or disease that damages the lymph nodes are lymphatic vessels
how is imaging useful for in lymphoedema?
confirm the diagnosis, plain surgery, intraoperatively
what is the pathology os lymph node enlargement?
may not cause an increase in lymph nodes size & lymph node enlargemtn is not always pathological
what are the causes of lymph nodes enlargement?
infection of lymph, reaction to immune resposes elesewhere in the body, neoplasia, drugs
what is the size of lymph nodes?
most nodes are 10mm- submental & submandibular (15mm)- retropharyngeal (8mm)
what is hypersensitivity?
excessive immune response- antigen specifc & can only after exposure to antigen
what is type I hypersensitivty?
immediate hypersensitivity reactions occurs within a few minutes (cause adverse reactions to contrast media)
what is type II hypersensitivity?
cytotoxic hypersensitivity reactions occurs after a few hours- cause myasthenia gravis & rheumatoid arthritis
what is type III hypersensitivity?
immune complex reactions occur after a few hours
what is type IV hypersensitivity?
delayed reactions occur after 24 to 72 hours
what are idiosyncratic reactions?
typically begin within 20 mins of injection & dose independent - produce same effects as anaphylaxis but not a true hypersensitivity reaction (previous sensation is not required & may not recur)
what increases risk to idiosyncratic reactions?
have previous history of reaction to contrast medium, asthma, other allergies
what are symptoms of idiosyncratic reaction?
hives (urticaria), itching (pruritus), runny nose (rhinorrhea), nausea, coughing, dizziness- severe symptoms (anaphylatic shock, broncospasm, laryngeal or pulmonary oedema, seizures, death)
what are nonidiosyncratic reactions?
contrast Can aggregate a # of underlying conditions
what are delayed reactions?
become apparent at least 30 minutes after but within 7 days of the ICM injection
what are symptoms of delayed reactions?
flulike symptoms, nausea, vomiting, diarrhoea, abdominal pain, dizziness, headache- resolve spontaneously
what is autoimmune disease?
immune system loses tolerance for self antigens leading to tissue destruction- due to genetic make up, infections, drugs - localised or systemic (either rheumatological or vascular)
what are localised autoimmune diseases?
addisons disease, coeliac disease, crohns disease, diabetes type 1, graves disease, multiple sclerosis, ulcerative disease
what are systemic autoimmune disease?
dermatomyositis, rheumatoid arthritis, scleroderma
what are immune deficiency disorders?
prevent your body from fighting infections and diseaseso primary or secondary
what are primary immunodeficiencies?
genetic & lead to various combinations of recurrent infections, autoimmunity, atopy, malignancy
what are secondary immunodefiencies?
caused by age (old or young), medications, procedures (splenectomy), infections, metabolic, nutrition related, misc (burns, malignancies, radiation therapy )
what is the function of the spleen?
immune responses, phagocytosis of red blood cells and microorganisms, haematopoiesis, red blood cell storage- located un left hypochondrium at level of 9th-11th ribs
what does the spleen contact?
diaphragm, anterior surface of the left kidney, splenic flexure of the colon, fundus of stomach, tail of pancreas
when evaluating the spleen, what should we ask?
is it present (may have been surgically removed), is it normal size (11 + 2cm) - is it ruptured, does it perfuse with contrast (non perfusing areas may indicate a blocked artery, abscess/infection, or tumour
what are common pathologies of the spleen?
splenomegaly & splenic trauma
what are common structural abnormalities of spleen?
accessory spleen or spenunculi formed from nodules that fail to fuse during development found in various locations through the abdomen, enlargement, asplenia (absence of spleen)
what can enlargement of spleen be due to?
infections (malaria), malignancies (lymphomas, leukemias), portal hypertensions, spleen often enlarges as it performed its normal functions
how can trauma of spleen be investigated?
plain radiographs (most common is left lower rib fractures)- CT (modality of choice with contrast)- clefts may mimic lacerations & splenic capsule will hold in blood from rubtured spleen
