Background: Previous findings regarding risk factors for human papillomavirus (HPV) persistence, other than viral determinants, identified from prospective cohort studies have been inconsistent in part because study designs have differed with respect to differing HPV detection methods and varying lengths of follow-up time. Therefore, the objectives of this study were to continue the search for epidemiologic risk factors of persistent cervical HPV infections and determine what behaviors differed between those women with transient HPV infections and those women who cannot clear their type-specific HPV infections. Methods: Female university students (n = 621) in Montreal were followed for 24 months at 6-month intervals. At each visit, a cervical cell specimen was collected. HPV DNA was detected using the MY09/MY11 PCR protocol and 27 HPV genotypes were identified by the line blot assay

THE rccovcry of pure Rh antiscra is usually effected by absorption of the unwanted antibodies froin iiiixturcs of antibodies, leaving the desired oiic behind. For example, the removal of anti-A and anti-B aiitibodics in an anti-Rh serum from an individual of group 0, is brought about either by absorption with group-A and group-B Rh-negative red cells or by neutralization with specific group-A aiid group-B substances. Careful testing is required to ensure the complctc removal of the unwanted antibodies from the absorbed serum. A disadvantage of this iiicthod is that the serum inevitably becomes to a greater or lesser degree dilutcd and a weak serum furthcr weakeiied during the process of absorption.The disadvantage of this procedure is avoided by elution of the Rh antibody after its specific absorption upon the appropriate red cells, and a new method of elution has been devised in which thc eluate may be used as an incomplete anti-Rh serum.In the coursc of investigating several methods of elution it was found that Kh antibodies attached to their spccific red cells could be recovercd by treatment with ether, the antigen being destroyed or denatured, while the antibody itself remained uiiaffected when the volatilc ether was removed. The resultant, sticky, haemoglobin-stained liquid could, however, bc used as a testing fluid in this condition only by the indirect antiglobulin method, and therefore lost many of its advantages over ail incomplete anti-Rh serum.The absorption and elution of a valuable but weak immune Rh antibody by the widely known method of Laiidsteiner and Miller (1925) often results either in the loss of part of the antibody owing to dilution with saline or in a poor yield from other causes. In some instances evcn an originally strong antibody is found, after elution, to give only a weak reaction by the iiidircct antiglobulin iiicthod. The new technique differs from that of Landsteiiier and Miller in that the antibody is recovered from the stromata into a neutral A,B serum, by treatment with ether, whereas by the older method heat is used to elute the wanted antibody from the cells into saline.Kidd's (1949) aiid Selwyn's (1952) methods of antibody elution gave inconstant results whcii compared with the stromata-ether-extract technique, and it was not possible to obtain stable preparations of Rh antibody eluates using their methods.kccntly, a valuable antiserum was encountered containing a mixture of the antibodies, anti-E, anti-c and anti-K, in addition to anti-B, in a group-A, CDe/CDe, K-iiegative woman. Using the iiew method to recover thc antibodies separately, the ser~liii was first trcatcd by thc addition of group-0 cde/cde K-negative cells. The anti-c was takeii up by the cclls which were removed by centrifugation, thoroughly washed and a specific iiicomplete anti-c serum prepared from them by the technique described below. The anti-E was then rcmovcd in a similar way using group-0 cDE/cDE or cDE,cde K-negative cells, having first madc sure that the anti-c had been completely absorbed. If CDej...

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