1215

2. The tendency to subpial demyelination of the spinal cord,forming either a narrow ribbon or wedge in transverse section; thebase of the wedge lies on the surface of the cord.3. The perivascular distribution of demyelination, in relation tothe veins and venules.4. The tendency to the formation of "dumb-bell" lesions whentwo venules occur in close proximity.5. The formation of lesions on either side of a cleft-ie, theso-called "kissing" lesions in the cord or cerebrum.6. The periventricular distribution of lesions.7. The undue vulnerability of the optic nerves.8. The special type of MS lesion in Balo’s disease where certainzones (which are almost certainly related to the anatomy of thevessels) escape demyelination, to leave a concentric appearance insome sections.9. The symmetry of affected areas, particularly in the spinal cord.All these indicate that at the sites of the lesions there are very

important local features which contribute to the process of

demyelination in MS. The unravelling of the mechanisms ofautoimmune demyelination in the CNS may provide importantclues about the similar processes in other organs which are less easyto examine histologically and perhaps to understanding the

"degenerative" diseases of the nervous system. ‘

I thank Prof Dudley C. Dumonde for help and encouragement; Dr MarianKies of the National Institutes of Health for gifts of myelin basic protein; MrTerence J. Bartlett for technical assistance; and Action for Research intoMultiple Sclerosis (ARMS) for their support.

Rayne Institute,St Thomas’ Hospital,London SE1 7EH JACK COLOVER

1. Colover J. A new pattern of spinal-cord demyelination in guinea pigs with experimentalallergic encephalomyelitis mimicking multiple sclerosis. Br J Exp Pathol 1980; 61:390-400.

2. Colover J Acute demyelination in EAE after pretreatment with foreign protein andmuramyl dipeptide (MDP). In: Alvord EA Jr, Kies MW, Suckling AJ, eds.Experimental allergic encephalomyelitis: A useful model for multiple sclerosis.New York: Alan R. Liss, 1984: 37-42.

3. Colover J. Distinctive spinal cord lesions in EAE in animals pretreated with ovalbuminand myramyl dipeptide. In: Huber A, Klein D, eds. Neurogenetics and neuro-ophthalmology. Amsterdam: Elsevier/North Holland, 1981: 103-06.

4 Cruveilhier J. Anatomie pathologique du corps humaine (32e livre). Paris: Baillière,1835-42: 22.

KISTLER/NITSCHMANN PLASMA FRACTIONATIONMETHODS

SIR,-Dr Hein and others (Feb 16, p 405) try to cast doubts on theplasma fractionation method of Kistler and Nitschmann (K/Nprocess)I,2; their comments are based on the transmission ofnon-A,non-B hepatitis by an experimental intravenous immunoglobulin(IVIG) preparation obtained by this fractionation method.3 Theirremarks are, however, both erroneous and misleading.Although ionic strength has, in the KIN process (and in the Cohn

process), a critical influence on the purity of the IgG, it is incorrectto infer that the K/N process is "less controlled"; a careful dosage ofthe buffer systems used allows us to obtain consistentlyreproducible results. The "higher quality and purity" of the IgGobtained by Cohn’s methods 64 and 95 compared with the IgGprepared by the K/N method, amounts to a difference in purity of 98and 97%, respectively. It is surprising that Hein and others mentionthe method of Hink et al6 as one of the modifications of Cohn’smethods which is used in the United States, since this represents amuch more drastic departure from Cohn’s original conditions thanthe K/N method does. Albumin prepared by Hink’s method has apurity of 85-90%, as compared with 97-99% for both Cohn andK/N albuminn.Readers not familiar with the methodology may get the

impression from Hein and colleagues’ letter that the K/N procedureis inherently less safe than the Cohn method, and possibly that theK/N process is related to the unsafe Cohn method 12-and thatthese are reasons why the US Food and Drug Administration shouldnot license products made by the K/N process. There is nothingmagic about the Cohn method; the assumption that Cohnfractionation products are safe, rests entirely on their long-standingrecord. The KIN method, which was developed in the early (not

late) 1950s has a similar record, on the basis of which the CentralLaboratory of the Swiss Red Cross has obtained FDA licences for itsalbumin and IVIG; so far, over 1500 kg of the.IVIG

(’Sandoglobulin’) has been used in clinics all over the world,sometimes in a very high dosage; no instance of transmission of anyinfectious disease has been reported.Despite the safety record of IgG prepared by the cold-ethanol

methods, isolated cases of transmission of hepatitis B have beenrecorded.7,8 One incident was investigated in great detail;8 thematerial had been prepared by an American manufacturer

according to methods 6 and 9 of Cohn4 and Oncley andtransmission of hepatitis to chimpanzees was proved. No such caseis known for the K/N method. Transmission of non-A, non-Bhepatitis has been reported for two experimental lots of IVIG-oneprepared in the UK by K/N fractionation,3,9 isolation beingfollowed by a treatment to make the product suitable forintravenous administration; the other, prepared by an AmericanmanufacturerlO starting from Cohn fraction 11,4,5 was a newlydeveloped preparation for intravenous application that was beingtested clinically. The reasons for the infectivity observed are unclearin both cases and the observations are in striking contrast withprevious experience.Experience so far has demonstrated the extraordinary safety of

both the Cohn4,5 and KlN1,2 processes; however, complete absenceof infectious agents cannot be guaranteed for either method. It istherefore still imperative to use raw material obtained from asegment of the population which does not carry an increased risk oftransmitting infectious diseases.

Central Laboratory,Swiss Red CrossBlood Transfusion Service,

CH-3000 Bern 22, Switzerland

H. FRIEDLI

J.-J. MORGENTHALER

1. Nitschmann H, Kistler P, Lergier W. Vereinfachtes Verfahren zur Gewinnung vonhumanem Albumin und gamm-Globulin aus Blutplasma mittels Alkoholfällung.Helv Chim Acta 1954; 37: 866-73.

2. Kistler P, Nitschmann H. Large scale production of human plasma fractions. Vox Sang1962; 7: 414-24.

3. Lever AML, Webster ADB, Brown D, Thomas HC. Non-A, non-B hepatitis afterintravenous gammaglobulin. Lancet 1985; i: 587.

4. Cohn EJ, Strong LE, Hughes WL, et al. Preparation and properties of serum andplasma proteins. J Am Chem Soc 1946; 68: 459-75.

5. Oncley JL, Melin M, Richert DS, et al The separation of antibodies, isoagglutinins,prothrombin, plasminogen, and beta-1-lipoprotein into subfractions of humanplasma. J Am Chem Soc 1949; 71: 541-50.

6. Hink JH, Hidalgo J, Seeberg VP, Johnson FF. Preparation and properties of a heat-treated human plasma protein fraction. Vox Sang 1957; 2: 174-86.

7. John TJ, Ninan GT, Rajagopalan MS, et al. Epidemic hepatitis B caused bycommercial human immunoglobulin. Lancet 1979; i: 1074.

8. Tabor E, Gerety R. Transmission of hepatitis B by immune serum globulin. Lancer1979; ii: 1293.

9. Lane RS Non-A, non-B hepatitis from intravenous immunoglobulin. Lancet 1983; ii:974-75.

10. Ochs HD, Fischer SH, Virant FS, et al Non-A, non-B hepatitis and intravenousimmunoglobulin. Lancet 1985; i: 404-05.

ANTIBODIES TO HEPATITIS A AND B VIRUSANTIGENS IN Rho (D) IMMUNE GLOBULIN

SIR,-We would like to comment on the article by Dr Tabor andcolleagues (Jan 5, p 46). We tested 23 lots of Rho (D) immuneglobulin (RhIG) for antibodies to the antigens of hepatitis A and Bviruses (HAV, HBV). These lots were released in 1983/84 by thePaul Ehrlich Institute, the Federal Government’s agency for seraand vaccines in the Federal Republic of Germany, and theyoriginated from six different manufacturers (7, 4, 4, 3, 3, 2). Abbottradioimmunoassays were used to test for hepatitis antibodies. Anti-HBs and anti-HAV were compared with the international referencepreparations from the WHO. Anti-HBe and anti-HBc werecompared also with a national reference preparation. All RhIG lotscontained anti-HBs, anti-HBc, and anti-HAV. 16 lots containedanti-HBe.The antibody profile (see table) of RhIG was not identical to that

reported by Tabor and colleagues. The antibody concentration wasscattered over a wider range, except for anti-HBe. These findingswere identical to those found in immune serum globulin (IgG).1>2 2

100 IU per ampoule of the international reference preparation of