An International Reference Preparation for Human Serum Immunoglobulin E*

Bull. Org. mond. Santd 11973, 49 320-321Bull. Wid Hlth Org. J An International Reference Preparation for Human Serum Immunoglobulin E * D. S. RowE,1 B. GRAB,2 & S. G. ANDERSON 3 Abstract Following a collaborative assay by five laboratories in four countries, an International Reference Prepara- tion for Human Serum Immunoglobulin E has been established by the World Health Organization and international units have been assigned to it. Immunoglobulin E forms a distinct class ofhuman immunoglobulins; antibodies of this class initiate reactions of immediate hypersensitivity such as those seen in asthma, hay fever, and some forms of food and drug allergy. Serum concentrations of IgE are often raised in allergic and parasitic diseases and measurements are useful in both clinical medicine and research. IgE can only be measured by immunochemical methods using specific antiserum. Sensitive methods are required since serum concentrations are lower than those of other immunoglobulin classes. In these methods, the amount of IgE as antigen is compared with that of the IgE in a standard. Establishment and unitage of the International Refer- ence Preparation In recent years, a standard for serum IgG, IgA, and IgM has been prepared in the form of pooled freeze-dried human serum and this material has been established as an International Reference Prepara- tion, as described by Rowe et al. (1). Pooled human serum of relatively high IgE content has been pre- pared in a similar way as a standard for IgE (code 69/204). This material has now been estab- * A full account of the preparation and assessment of the International Preparation, of which this Brief Communica- tion is a summary, has been deposited in the WHO Library. Single photocopies may be obtained by professionally interested persons on request to: Chief Librarian, World Health Organization, 1211 Geneva 27, Switzerland. 1 Director, WHO International Reference Centre for Immunoglobulins, Lausanne, Switzerland. 'Health Statistical Methodology, World Health Organiza- tion, Geneva, Switzerland. ' National Institute for Biological Standards and Control, Holly Hill, Hampstead, London, England. lished as the International Reference Preparation of Human Immunoglobulin IgE by the WHO Expert Committee on Biological Standardization (2), which also defined the international unit of IgE as the activity contained in 0.006562 mg of the dried pow- dered serum. For all practical purposes there are 11 500 international units per ampoule. A research standard for IgE (68/341) had previously been pre- pared by the National Institute of Biological Stan- dards and Control (NIBSC), London, England; this has been described by Rowe et al. (3) and units have been assigned to the preparation. This material has now been designated as the NIBSC standard for IgE (68/341). The Expert Committee took note of the estimated figure of 11 566 units per ampoule obtained by comparison of the International Refer- ence Preparation (69/204) with the NIBSC standard (68/341) but rounded off this figure in assigning the unitage. There is thus a negligible difference between the units defined by the NIBSC standard (68/341) and the international units defined by the Inter- national Reference Preparation. Method ofpreparation and assessment e method of preparation and assessment of the In brnational Reference Preparation was similar to tb,at described by Rowe et al. (4) for the Inter- national Reference Preparation for human serum immunoglobulins IgG, IgA and IgM. The serum pool was derived from serum obtained in Sweden and Africa. Studies by 5 laboratories in 4 countries showed that the IgE was stable as an antigen and that measurements of the IgE content of 10 serum samples against the International Reference Prepara- tion by the different laboratories using several tech- niques were in reasonable agreement. Subsequently, several laboratories have shown that the International Reference Preparation contains hepatitis-B associated antigen. For this reason, it is likely that another similar preparation of IgE free of hepatitis-B associated antigen will be produced and calibrated against the International Reference Prep- aration. 3120 - 320- BRIEF COMMUNICATIONS Availability of the International Reference Preparation A number of ampoules of the International Refer- ence Preparation are being held at the WHO Inter- national Laboratoryfor Biological Standards, Statens Seruminstitut, Copenhagen, Denmark, for ultimate reference purposes, and for the calibration of na- tional reference preparations. Investigators in the Americas who require the International Reference Preparation or a related preparation for use in their own laboratories should apply to the Director, WHO Regional Reference Centre for Immunoglobulins, National Cancer Insti- tute, Bethesda, Md. 20014, USA. Workers in the United Kingdom should direct requests to the Director, National Institute for Biological Standards and Control, Holly Hill, Hampstead, London NW3 6RB, England. Workers elsewhere should direct requests to the Director, WHO International Refer- ence Centre for Immunoglobulins, 21, rue du Bugnon, 1011 Lausanne, Switzerland. Letters ofrequest should include a statement that the applicant is aware that the preparation contains hepatitis-B associated anti- gen and will take appropriate precautions in handling the material in the laboratory. Recommendations for the use of the International Reference Preparation 1. On receipt the Reference Preparation should be stored at -20°C. 2. 1 ampoule of the Reference Preparation should be reconstituted by the addi.ion of 1 ml of distilled water. The powder should dissolve readily on stand- ing at room temperature. An appropriate series of dilutions of this solution should be prepared and used on the same day that the material is recon- stituted. 3. The total volume of the solution of this prep- aration made in this way will exceed 1 ml. It has been calculated that this solution will contain 10 948 inter- national units per ml. 4. IgE in the solution under test should be assayed against the International Reference Preparation or related preparations by techniques that have been validated statistically. 5. The relative potency should be expressed in international units of activity of IgE per ml of solution, or per mg of dry substance. 6. Since the International Reference Preparation is not available in quantities sufficient for inclusion in every titration run, it is recommended that for this purpose local standards be prepared and cali- brated against the International Reference Prepara- tion or related preparations. 7. Since the preparation has been shown to con- tain hepatitis-B associated antigen, it should be handled with appropriate precautions. REFERENCES 1. RowE, D. S. ET AL. A research standard for human serum immunoglobulin IgG, IgA and IgM. Bull. Wld Hlth Org., 42 (4): 535-552 (1970). 2. WHO EXPERT COMMITTEE ON BIOLOGICAL STANDARD- IZATION. Twenty-fifth report. Wld Hlth Org. techn. Rep. Ser., No. 530, p. 10 (1973). 3. ROWE, D. S. ET AL. A research standard for human serum immunoglobulin E. Bull. Wld Hlth Org., 43 (4): 609-611 (1970). 4. RoWE, D. S. ET AL. An international reference pre- paration for human serum immunoglobulins G, A and M: content of immunoglobulins by weight. Bull. Wld Hlth Org., 46 (1): 67-79 (1972). PARTICIPANTS IN THE COLLABORATIVE ASSAY NETHERLANDS Dr E. E. Reerink-Brongers & Mr. R. G. Aalberse Central Laboratory Netherlands Red Cross Blood Transfusion Service P.O. Box 9190 Amsterdam W SWEDEN Dr M. Ceska Pharmacia A.B. Box 604 S750-14 Uppsala Dr S. G. 0. Johansson The Blood Centre University Hospital S750-14 Uppsala SWITZERLAND Dr D. S. Rowe WHO International Reference Centre for Immunoglobulins Universite de Lausanne 21, rue du Bugnon 1011 Lausanne UNITED STATES OF AMERICA Dr Kimishige Ishizaka The Johns Hopkins University Medicine and Microbiology Dept. School of Medicine The Good Samaritan Hospital 5601 Rock Raven Boulevard Baltimore, Md. 21212 321