Immunology - short notes for GPs!
Dr. Joanna Sheldon, Protein Reference Unit, St. George's Hospital
April 2014
The immune system: a complex interaction between cells (esp. white blood cells), soluble
immunological mediators (immunoglobulins, complement, acute phase proteins, other mediators) and
lymphoid tissue or organs (bone marrow, spleen, thymus etc). Lots can go wrong – not enough of a
particular component being produced or too much being destroyed resulting in IMMUNEDEFICIENCY.
A MALIGNANCY of one of the cell types – lymphoid malignancy includes B cell malignancies such as
multiple myeloma, lymphoma, CLL or Waldenstroms macroglobulinaemia. Components doing the wrong
thing resulting in HYPERSENSITIVITY (Type I a.k.a. allergy or type II or III a.k.a. autoimmune disease or
type IV or delayed type hypersensitivity). The immune system is also important in vaccination and in
tissue typing for transplantation.
Dr. Joanna Sheldon contact details – 0208 725 0025
 Most “routine” tests e.g. ANA are done daily  more complex tests weekly  rare tests done when
required  phone us if you have a question  if you are not sure what test you want, put the disease that
you want to exclude or diagnose - we can do the most appropriate tests  some tests need special
collection e.g. cryoproteins - call the lab to arrange  7ml plain tube is usually enough for all tests  no
test has 100% specificity and 100% sensitivity for disease – Immunology tests often show both false
negative and false positive results  tests can be consistent with or suggestive of a disease, part of the
diagnostic criteria, used in assessment of disease prognosis or useful to monitor the disease  when
monitoring monthly, quarterly or even less frequently is most appropriate NOT daily or weekly  only a
few immunological analytes are useful for disease monitoring  numerical results are reported with
appropriate age related reference range - essential for interpretation  immunology testing is generally
expensive so use carefully!
 Rheumatoid Factor - antibodies against the constant portion of other antibodies - usually IgM
antibodies against the Fc portion of IgG. RF is NOT specific for rheumatoid arthritis although higher the
concentration, closer the association with RA. Positive RF seen in the elderly, in patients with chronic
infections or inflammatory processes, in B cell malignancy. Not very helpful for monitoring RA - better to
use CRP.
Anti CCP antibodies are the new exciting test – but NICE say refer the patient to
Rheumatology if you think they have RA rather than doing lots of tests.
 Antinuclear antibodies (ANA) - IgG antibodies to components of the cell nucleus e.g. DNA (double
and single stranded), proteins and enzymes associated with nuclear functions. These nuclear
components are distributed in the nucleus either homogeneously (DNA), in chromosomes (double
stranded DNA) or in little clumps speckled throughout the nucleus (the Extractable Nuclear Antigens or
ENAs). We look at three things - nuclear staining, homogeneous or speckled, chromosomes staining?
No nuclear staining - ANA negative. Homogeneous pattern - check specific antibodies to dsDNA especially if chromosome staining is seen. Speckled pattern - check for antibodies to the ENAs. There
are only a few clinically relevant ENAs – antibodies to ss (Sjogrens syndrome) A and B a.k.a. Ro and La.
Anti Ro antibodies can cause foetal heart block. Anti Sm is very specific for SLE (but not sensitive). Anti
RNP antibodies are seen in mixed connective tissue disease. Weak positive ANA are often seen in
infections (usually viral), chronic inflammatory conditions, more commonly in women than men, and in
aged patients.
Low titre ANAs (1/80) are usually non-specific findings or associated with
infection/inflammation. We can check for dsDNA or ENA antibodies but usually suggest you follow-up in
3-6 months (sooner only if clinically indicated) to see whether it has increased in concentration or
disappeared.
 Anti neutrophil cytoplasmic antibodies (ANCA) - IgG antibodies to enzymes in the cytoplasm of
neutrophils. ANCA are associated with vasculitic disorders - both in diagnosis and monitoring. The
enzymes have slightly different cytoplasmic distribution in lab neutrophils - Proteinase III is evenly
spread around the cytoplasm - Anti PRIII antibodies give a c(cytoplasmic)-ANCA pattern.
Myeloperoxidase is localised around the nucleus - Anti MPO antibodies give a p(perinuclear)-ANCA
pattern. c-ANCA and anti PRIII antibodies are associated with small vessel vasculitis e.g. Wegener's
granulomatosis and microscopic polyarteritis. p-ANCA and anti MPO antibodies are seen in PAN,
Churg Strauss and rheumatoid vasculitis. There are other ANCA specificities but not in routine use.
Serial monitoring of the anti PRIII or the anti MPO may be useful in monitoring.
When investigating a patient with deteriorating or poor renal function, if you ask for an ANCA you should
also consider anti Glomerular Basement Membrane antibodies (GBM) - they are associated with
Goodpastures syndrome and patients may have very similar symptoms. ANCA and GBM antibodies
would usually be requested for hospital in-patients or via Medical/renal admitting firms.
 Immunoglobulins and electrophoresis - Immunoglobulins behave as acute phase proteins and
their concentration changes in numerous diseases; there are really only two clear indications for
measuring Igs and doing electrophoresis 1. investigation of suspected immune deficiency and 2.
investigation of suspected B cell malignancy.
Consider Immune deficiency (ID) in any patient with repeated, severe, atypical infections. In adults, ID
is most likely to be secondary to protein loss, malnutrition, cytotoxic treatment, immune suppression,
infection, malignancy. Check IgG,A,M, albumin and protein EP. Primary ID is rare (IgA deficiency is the
most common 1/700 of pop - many are asymptomatic) but there is a risk of developing IgA antibodies if
given blood products and anaphylaxis on next exposure to IgA containing products. Common Variable
ID worth considering in patients with bronchiectasis - IgG,A and M are usually all low and low-normal
lymphocyte counts. IVIG is usually treatment and use IgG to monitor - patients with CVID have
increased risk of autoimmune disease and malignancy. IgG has 4 subclasses and you can get isolated
deficiencies of these - particularly IgG2 and IgG4 - measure if you have a normal IgG concentration but
clinical suggestion of immune deficiency. Also consider complement components for recurrent
meningitis - neisserial meningitidis infections are more common in patients with C6 deficiency - ask for
CH50 - low in most complement deficiencies – generally specialist immunology requests.
When considering lymphoid malignancy you should ALWAYS check SERUM AND URINE for
paraprotein. Incidence of Ig classes in paraproteins is IgG>IgA>IgM>kappa>lambda>IgD>IgE. Kappa
and lambda are the light chains and if MONOCLONAL are called Bence Jones protein. IgM paraproteins
(big molecule, intravascular - can give hyperviscosity) usually result from tumours earlier in B cell
progression - e.g. Waldenstroms macroglobulinaemia, CLL, lymphoma. Paraprotein types in myeloma:
IgG>IgA>Bence Jones protein ( or  are approx 20% of all myelomas) IgD (approx 3% of myelomas).
BJP is small and passes easily through the glomerulus so you can miss BJ only myelomas if you only
look in the serum - usually you see low serum IgG,A and M and a monoclonal band on the urine EP. BJ
only and IgD myelomas are usually more aggressive. Diagnosis of myeloma - 2/3 of pp in serum and/or
urine, lytic lesions on X-ray survey, abnormal numbers of plasma cells in BM. Paraproteins are also
seen in benign disease, secondary to infection, in monoclonal gammopathy of unknown significance and
with increasing prevalence in the elderly population. Small paraproteins can be incidental findings,
particularly in the elderly - check concentration of paraprotein, presence of immune suppression, albumin
concentration, presence of BJP in urine, renal function, 2microglobulin - powerful prognostic indicator in
myeloma. Monitor paraprotein concentration, immune suppression, renal function, haematology.
 IgE and Allergy - an increasing problem. A good history is essential in identifying the possible
allergens. Check what symptoms and when - pollen season, not winter - pollen allergy. Trees flower
followed by grasses then weeds. Symptoms all year - house dust mite, feathers. For respiratory
allergies, skin testing is the most appropriate investigation but you can do specific IgE. Skin testing must
be done with resuscitation facilities available - it may be contraindicated if the patient has ever had a
severe reaction. It can be difficult to skin test if the patient is a baby/child, if the patient has significant
skin problems, it is unreliable if the patient is on anti-histamines and it lacks sensitivity for food allergies.
Not all reactions are IgE mediated - e.g. strawberries, chocolate and wine can be direct pharmacologic
effects. Most allergens have been reported to cause anaphylaxis - the most common are Penicillin,
wasp and bee venom, peanuts, latex, egg, fish and shellfish.

Other diseases where Immunology tests can be useful!
- Coeliac disease - endomysial antibodies (also tissue transglutaminase) see NICE guidelines
- Pernicious anaemia - intrinsic factor antibodies
- Graves disease - TSH receptor antibodies
- Hashimotos - thyroid peroxidase (or microsomal) antibodies – not helpful if TFTs are abnormal
- Primary biliary cirrhosis - mitochondrial antibodies (and raised IgM)
- Rheumatoid arthritis - rheumatoid factor (ANA may also be positive) see NICE guidelines
- Bullous skin diseases - skin basement membrane or intercellular cement
- Complement - renal disease in SLE or active immune complex disease