The Rheumatoid Factor

The observation that certain human sera had the property of agglutinating sheep erythrocytes previously sensitized with specific antibody has been made sporadically since the turn of the century. Only in 1940, however, was this property shown to belong, in the main, to sera from patients suffering from rheumatoid arthritis. In that year, Waaler, (1) working in Scandinavia, published a paper drawing attention to the phenomenon and described a serological test claimed to be useful in the diagnosis of rheumatoid arthritis. Because of the difficulties of communication in war-time, Waaler’s work remained largely unknown. In 1948, Rose and his colleagues (21) in New York, unaware of Waaler’s observations, “rediscovered” the phenomenon and described a diagnostic test, similar in principle to Waaler’s. The observations of Waaler and of Rose and his colleagues have now been amply confirmed and the Rose Waaler test, or more usually one of the numerous modifications thereof, is used routinely as a diagnostic aid in rheumatoid arthritis. Copyright Royal Medical Society. All rights reserved. The copyright is retained by the author and the Royal Medical Society, except where explicitly otherwise stated. Scans have been produced by the Digital Imaging Unit at Edinburgh University Library. Res Medica is supported by the University of Edinburgh’s Journal Hosting Service: http://journals.ed.ac.uk ISSN: 2051-7580 (Online) ISSN: 0482-3206 (Print) Res Medica is published by the Royal Medical Society, 5/5 Bristo Square, Edinburgh, EH8 9AL Res Medica, Winter 1967-68, 6(1): 17-19 doi: 10.2218/resmedica.v6i1.829 THE RHEUMATOID FACTOR by W. R. M. ALEX AN D ER Rheum atic Diseases Unit, Northern G eneral Hospital. Edinburgh

T h e observation that certain human sera had the property of agglutinating sheep erythrocytes previously sensitized with specific antibody has been m ade sporadically since the turn of the century.
O nly in 1940, however, was this property shown to belong, in the m ain, to sera from patients suffering from rheumatoid arthritis.In that year, W a a ler,(1) working in Scandinavia, published a paper drawing attention to the phenom enon and described a serological test claim ed to be useful in the diagnosis of rheumatoid arthritis.Because of the difficulties of com m unication in war-time, W aaler's work remained largely unknown.I n 1948, Rose and his colleagues(21) in N ew York, unaware o f W a a ler's observations, " rediscovered" the phenom enon and described a diagnostic test, sim ilar in principle to W a a ler's.T h e observations of W aaler and of R ose and his colleagues have now been am ply confirmed and the Rose W aaler test, or m ore usually one of the num erous m odifications thereof, is used routinely as a diagnostic aid in rheum atoid arthritis.

TH E ROSE W A A L E R T E S T A N D ITS D E R IV A T IV E S
In the original test, com plem ent is removed from the test serum by heating at ;6 °C .for thirty m inutes.D uplicate serial dilutions o f the serum are m ade and to one set of dilutions sheep erythrocytes, previously washed in saline, are added.T h is titration gives some measure of the concentration of heterophil agglutinins which are alm ost invariably present in human sera.T o the other set of dilutions, sheep erythrocytes which have been sensitized with a sub-agglutinating dose of rabbit anti-sheep erythrocyte serum are added.*A fter a period o f incubation at 3 7 °C .the titre of the test serum for non-sensitized and sensitized sheep erythrocytes is read.A s an exam ple, using serum from a healthy subject th e titre for non-sensitized sheep cells m ight be 1 : 32 and that for sensitized sheep cells 1 : 64.In expressing the result of the test the recipro cal of the titre for sensitized cells is divided by the reciprocal of the titre for non-sensitized cells, in this instance, 64 divided by 32 = 2. T h e quotient is called the differential agglutination titre or D .A .T .A D .A .T . of 8 or m ore is generally taken to be a positive test indicating that in rheum atoid arthritis the titre of the serum for sensitized cells usually greatly exceeds the titre for non-sensitized cells.T h is original test is technically satisfactory, but suffers from th e drawback that a " false negative" Result m ay be obtained in a patient with rheum atoid arthritis if a high titre of heterophil agglutinins is present.
B a ll3) in 1950, proposed a m odification to the original test to overcom e this difficulty.In his test, the serum is first absorbed w ith nonsensitized cells to rem ove heterophil agglutinins and then titrated with sensitized cells.T h e result is expressed as the true titre for sensitized cells.Mis m ethod is now generally preferred to the original R ose W aaler m ethod and the test has becom e known as the sensitized sheep cell test, S .S .C .T .or sheep cell agglutination test, S .C .A .T .
T h ere have been m any attem pts to increase the specificity and sensitivity of the S .S .C .T ., but, in general, it can be said that so far as practical tests for use in a routine laboratory are concerned, any increase in sensitivity is off set by a decrease in specificity.

R h eu m atoid A rthritis.
T h e test is positive in about 65. to 70 per cent of patients with adult rheumatoid arthritis.
Unfortunately, from the diagnostic point of view, the incidence is considerably lower in patients in whom the duration of the disease is less than one year and in whom certain other stigmata of rheumatoid arthritis, such as the presence of radiographic erosions or of subcutaneous nodules, are absent.
Prospective studies have shown that about one-third of patients remain sero-negative throughout the course of the disease, a further third m ay fluctuate from positive to negative and a third remain consistently sero-positive.

Polyarthritis, other than R h eu m atoid Arthritis.
T h e incidence of positive tests in juvenile rheumatoid arthritis (Still's disease) is low, ranging from about 7 to 15 per cent.Patients with ankylosing spondylitis, R eiter's disease, rheumatic fever, psoriatic arthritis, etc. arc generally sero-negative, the incidence of positivity being little greater than in the population as a whole.T h e incidcnce of scropositivity in other m em bers of the group of inflam m atory diseases o f connective tissue, (including dissem inated lupus erythematosus, progressive systemic sclerosis, polyarteritis nodosa and derm atom yositis), is difficult to establish in view of the clinical overlap between these conditions and rheumatoid arthritis.Sero-positivity is m ost likely to occur in cases of these diseases in which polyarthritis is a prom inent m anifestation.
O th er diseases and healthy subjects.In most reported series, the incidence of sero-positivity in diseases outwith the connective tissue group is around 4 to 5 per cent, this being no higher than in the population as a whole.' T h ere are, however, notable exceptions.Positive tests are frequently; recorded during the active phase of sub-acute bacterial endocarditis.T h e test is also postive in about 30 per cent of patients with leprosy and in a smaller proportion of patients suffering from the rather obscure group of diseases characterised by dysgammaglobulinaeinia.
About 5 per cent of apparently healthy individuals are sero-positive, b u t a higher figure is reported in the relatives of patients suffering from sero-positive rheumatoid arthritis.T h is latter observation has been advanced in support of there being a genetic factor in the patho genesis of rheumatoid arthritis, but could equally be accounted for by an environm ental factor.

THE NATURE OF THE FACTOR RESPONSIBLE FOR
AGGLUTINATION OF SENSITIZED SHEEP ERYTHROCYTES Rheum atoid factor (R.F1'.) has now been characterised by physicochem ical m ethods.T h e factor has been shown to be a high m olecular weight globulin belonging to the im m unoglobulin M (IgM ) class.It is m ost frequently detected in serum, but may also be present in synovial fluid and in other serous effusions in patients with rheumatoid arthritis.
U sing imm uno-chem ical m ethods, R .F .has been dem onstrated in plasma cells in synovial m embrane and in lym ph nodes.It has m any of th e characteristics of an antibody and form s complexes with globulins of the immuno-globulin G (Ig G ) class, provided that the Ig G has been denatured by physical or chemical means or, in the case of antibody Ig G , com bined w ith its specific antigen.O n the basis of animal experim ents, G lyn n , H olborow and Johnson*41 in 1957, suggested that R .F .reacted with sites on the gam m aglobulin m olecule which only became revealed when the m olecule was de natured.
W h e n the globulins in the serum of a patient with scro-positive rheumatoid arthritis are separated by ultra-centrifugation, precipitation will only rarely occur when th e Ig G and IgM fractions are recom bined.If, however, the Ig G fraction is heated at 6 o °C .for ten m inutes, and is then added to the IgM fraction .(whichcontains rheumatoid factor), precipitation occurs.On the basis of this experim ent, it has.been suggested that rheumatoid factor is not only an antibody but an auto-antibody.T h ere is, however, no clear-cut evidence that rheumatoid factor com bines with native -gam m aglobulin in vivo.
T h e ability of rheumatoid factor to precipitate w ith denatured Ig G form s the basis of the latex fixation test ( L .F .T .) .L a te x particles coated w ith denatu red hum an Ig G are clu m ped by scrum co n tain in g R .F .T h e L .F .T . is sim ple to do an d is m ore sen sitive than the S .S .C .T .but is, how ever, less specific fo r rheum atoid arthritis.

POSSIBLE PATHOGENIC SIGNIFICANCE OF THE RHEUMATOID FACTOR
There is n ow a con siderab le b o d y o f opin ion w h ich favours th e view that rheu m atoid arth ritis is an au to -im m u n e disease.T h is is not the place to discuss th e m erits and d em erits of such a hypothesis b u t rather to exam in e the possib le role o f R .F . in th e pathogenesis o f the disease.
It seem s reasonable to suppose that R .F . is pro duced b y the im m u n e system in response to stim u latio n by the presence in tissues of m ild ly altered Ig G .T h e re is evid en ce that Ig G is present in th e synovial lesion and it has been suggested th a t its presence in dicates an im m u n e reaction, p o ssib ly o f fu n d am en tal im portan ce, o ccurrin g in the syn oviu m .I f such a reaction should b e d em on strated in the fu tu re, it is likely that it w ill be show n to be o f th e cellm ed iated or d elayed h yp ersen sitivity type, for it is w ith this type o f im m u n e reaction that the h istological appearan ces in the synovial m em bran e arc m ost co m p atib le.
T h e suggestion that R .F . is n o t responsible for the synovial lesion in rh eu m atoid disease is b orne ou t b y a n u m b er o f ob servations.In 19 59, V a u g h a n and H a rris5 transfused hightitre rheu m atoid serum to oth er patien ts w ith the disease and failed to p ro m o te exacerbation o f sym p tom s.A lso, rh eu m atoid facto r has been sh ow n , som etim es in high titre, in un affected relatives o f patien ts w ith rheu m atoid arthritis and, from tim e to tim e, in th e sera o f appar en tly health y sub jects.H isto lo gically, it is im possib le to distin gu ish b etw een se ro-positive and sero-negative arthritis.A n arthritis, very sim ilar to rheu m atoid arthritis, occurs in patien ts su fferin g from h yp ogam m aglo bu linaem ia b u t no R .F . is found in the sera o f these patien ts.D u th ie , B ro w n , K n o x and T h o m ps o n ,6 in a stu d y o f the prognosis o f rh eu matoid arthritis, show ed that patien ts w ho w ere con sisten tly sero-positive fared w orse than their se ro-neg a tive fellow s.It can be suggested from this that in patien ts w ith co n tin u in g active disease, th e stim u lu s to the p ro duction o f R .F .by th e p rim ary synovial lesion is co n stan tly present.
A lth o u gh in th e m ain , the evid en ce is that R .F . is an in dicator, rather than m ediator, o f the p rim ary lesion , there is on e m an ifestation o f rheu m atoid disease w h ich cou ld b e caused by circu latin g R .T h e se observations, taken w ith the obvious c o m p a tib ility o f th e clin ical features and course o f rh eu m atoid arthritis w ith a ch ron ic in fe ctious illness, have re-aw akened in terest in the search fo r an exogenou s livin g an tigen in the synovial m em bran e. O ver the past few years a num ber of centres have reported isolation of a variety o f in fe ctive agents from rheu m atoid tissues.A lth o u g h non e o f these agents has been cau sally im p licated in the disease, th ere is n ow enough circu m stan tial evid en ce to extend this type o f in vestigation .Sh o u ld it even tu ally be established that rheu m atoid arthritis is caused b y a virus, m ycoplasm a or bacterium (or an y co m b in atio n o f the three!) then hopes o f a " cu re" w ou ld b e revived and those w ho find it difficu lt to b elieve that in dividu als turn against them selves -at least w ith ou t som e outside stim ulus -w ould be satisfied.
THE RHEUMATOID FA C T O R by W. R. M. ALEXANDER Rheum atic Diseases Unit, N orthern G en eral Hospital.Edinburgh H IS T O R IC A L F .It has been show n in exper im en tal an im als that in jectio n o f co m p lexes o f R .F .and denatu red Ig G in to th e m esen teric vessels m ay be fo llo w ed b y d eposition o f co mplexes in the term inal vessels, thus pro d u cin g a vasculitis.It seem s p ossib le that a sim ilar m echanism m ig h t acco u n t fo r th e vascular lesions seen in som e patien ts w ith rheu m atoid arthritis, p articu larly as it is co m m o n to find a very high titre o f R .F . in such patien ts.F in a lly , alth o u g h our kn ow led g e o f the p ath ogen ic sign ifican ce o f R .F . is in com p lete, tw o ob servations m ay give a lead to the aetiology o f rh eu m atoid arthritis.T h e first, already m en tion ed , is th e high in cid en ce o f R .F . in a few diseases of k n o w n in fe ctiv e aetiolo gy and the second is the d em on stration o f A b ru zzo and C h ristia n 17' that an " R .F .-like " substance m ay be d etected in th e serum o f anim als h yp crim m u n ised w ith dead b acteria.
A A L E R .E. (1940).A c ta p a t h , m ic r o b io l. S c a n d ..
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