K. Lennert

Toxoplasmosis is a ubiquitous infection, contracted by at least a third of the population in most areas of the globe. Clinical disease arises rarely, usually unexpectedly, but sometimes with disastrous effects on the patient. Humans, pets, farm and zoo animals may contract toxoplasmosis, possibly involving any clinical laboratory in its diagnosis. Pathologists must ponder the clinical significance of a hyperplastic l. ymph node, a cyst found at autopsy, or a serologic titer. Serving as scientific physicians, pathologists are asked: How is toxoplasmosis diagnosed? 'What is the treatment for ocular toxoplasmosis, for congenital infection, or for toxoplasmosis in the immunologically compromised host? vVhy does disease develop in as diverse areas as the eye, lymph nodes and placenta? How is Toxoplasma transmitted? This review proposes to survey recent advances, providing a scientific background to diagnose and manage the clinical problems of toxoplasmosis. Reviews are available which emphasize other aspects, such as serologic pro- cedures, resistance and immunity (REMINGTON, 1970), the clinical syndromes (DESMONTS, '1969; FELDMAN, 1968) and comprehensive presentations (JACOBS, 1967; FRENI{EL, '1970). Transmission and Prevalence The recent discovery of the coccidian stages of Toxoplasma in the cat intestine and the Toxoplasma oocyst excreted in cat feces, considerably broadens our understanding of Toxoplasma and its transmission (FRENKEL, DUBEY and MILLER, 1970).

The patriarch of experimental pancreas research is REIGNIER DE GRAAF (1641-1673). He carried out the first experiments with dogs in order to ob­ tain fistular secretion (1664). But only few years later, the just arisen interest in the physiology of the pancreas was severely set back by remarks of CONRAD BRUNNER. In 1682, BRUNNER expressed his belief that on the basis of experi­ ments he had carried out the pancreas was a vitally unimportant organ. He overlooked that after ligation of the main duct (discovered in the turkey by HOFMAN in 1641 and in a human cadaver by WIRSUNG in 1642), in the dog an accessory duct (described by SANTORINI in 1724) usually maintains an adequate flow of secretion. EBERLE in his monograph (1834) confirmed the emulsifying capacity of the pancreatic juice which had already been suggested by SYLVIUS (FRAN­ CISCUS DE LE BOE, 1614-1672) and he dealt with the essential enzymatic functions of the pancreatic juice such as amylolysis, lipolysis and proteolysis. Since HEIDENHAIN (1875), we know that for example trypsin (largely isolated by KUHNE in 1867) is situated in the acinar epithelial cells as zymogen in inactive form; it is thought that the action of "acid" on the glandular tissue is needed for inducing the "enzymatic activity". According to what we know now about the central role of acidosis in the activation of zymogen this topic is, of course, of topical interest.

Noch bis vor wenigen Jahren galt der Monocyt als der Lohengrin des Blutes: niemand wusste, woher er stammt. Dualist oder Trialist zu sein, war danach mehr eine Sache des Glaubens als des Wissens. Die enzym- histochemischen Untersuchungen von L.-D. LEDER haben - zusammen mit anderen aktuellen Forschungen zur Monocytengenese - den Beweis erbracht, dass der Monocyt aus dem Knochenmark und zwar aus der granulopoetischen Reihe abzuleiten ist. Der Trialismus ist somit gegen- standslos geworden. Die Ableitung des Monocyten aus dem Knochenmark hat auch fur die Nomenklatur der malignen Hamoblastosen einige Konsequenzen: Eine Form der sog. Reticulosen, die "histiomonocytare Reticulose", ist zu streichen. Die Hamoblastose der Monocyten ist keine Erkrankung des Reticulum, sondern eine Spezialform der myeloischen Leukamie, die man in ihrer reinen Form als Monocytenleukamie bezeichnen muss. Die Unter- scheidung eines Typus Naegeli und Schilling ist bei Anwendung enzym- histochemischer Kriterien hinfallig. Die Bedeutung des Monocyten bei der Entzundung, insbesondere bei der akuten Entzundung, wurde in den meisten Schulen sehr niedrig ein- geschatzt, ja neuerdings sollten die Lymphocyten als "Westentaschen- Makrophagen" auf dem Entzundungsfeld erscheinen und in wenigen Stun- den zu "Histiocyten" transformiert werden. Hier haben die Untersuchungen LEDERs, u. a. mit der Rebuckschen Hautfenstertechnik, eine klare Aussage ermoeglicht: Die Makrophagen der akuten Entzundung stellen zumindest zum allergroessten Teil emigrierte Monocyten dar. Eine Umwandlung aus- gewanderter Lymphocyten erfolgt nicht, gewebsstandige Histiocyten spie- len keine oder andernfalls eine untergeordnete Rolle.

,,1m Kleinsten die wirkliche Wahrheit gibt graBen Gedanken erst Klarheit" KARL THOMAS Each year sees the publication of hundreds of reports of experimental work on the lymphatic tissue, yet morphological studies of the cells involved can be counted on the fingers of one hand. Furthermore, anyone who tries to identify these cells by morphological criteria is accused of sophistry and hair­ splitting, whereas it is accounted scientifically correct and unbiased to speak of "lymphoid cells", "blast cells" etc. Not so many years ago things were different: there were too many names and too many classifi­ cations and everyone backed his particular fancy. People thought of cells in terms of rigid classes, nothing then being known about the transformability of mononuclear blood cells. Today we must look for the middle way: cells should be named and defined according to morpho­ logical criteria but their transformation potential should be borne in mind. Once the cells are analysed and subdivided, it will be simple enough to set up proper classifications afterwards. This book arose out of the conviction that there should be more criteria and more information available on the morphology of human lymphoreticular cells; previously such information had been restricted by the difficulty of the special hematological and cytochemical staining methods.

Kurz nach Erscheinen unseres Handbuchs iiber die Non-Hodgkin-Lymphome wurden Stimmen laut, die nach einem klein en handlichen AbriB der Lymphom- diagnostik riefen. Auch die Mitglieder des Europiiischen Lymphom-Clubs (1. DIEBOLD, Paris, R. GERARD-MARCHANT, Villejuif, Y. KAPANCI, Genf, G. KE- LENYI, Pecs, H. NOEL, Briissel, F. RILKE, Mailand, A. G. STANSFELD, London, und J. A. M. VAN UNNIK, Utrecht) bestiirkten mich darin, einen solchen Ratgeber fUr den diagnostischen Alltag zu schreiben. Ja sie identifizierten sich mit diesem Plan und stell ten sich fUr die Obersetzung in mehrere Sprachen zur VerfUgung. So habe ich J. DIEBOLD, R. GERARD-MARCHANT, F. RILKE und A. G. STANSFELD fUr die prompte Obertragung ins Franzosische, Italienische und Englische zu danken. F. RILKE iibernahm die Initiative, einen Beitrag zur "Working Formula- tion for Clinical Usage" zu verfassen. Obersetzungen in weitere Fremdsprachen wurden von ehemaligen Mitarbeitern und befreundeten Kollegen bereitwillig durchgefUhrt, so von A. LLOMBART BOSCH ins Spanische, von IRENE LORAND und J. M. MACHADO ins Portugiesische und von N. MOHRI ins Japanische. Das Erscheinen in verschiedenen Sprachen einschlief3lich meiner Muttersprache sollte den Gebrauch des Abrisses im Alltag we iter erleichtern.

The 1st Edition of Histopathology of Non-Hodgkin's Lymphomas, written in col­ laboration with Professor H. STEIN and published in 1981, was received well and is now out of print. In the meantime, there has been an explosion of data that not only have made the definitions of various entities more precise but, above all, have confirmed the main entities originally delineated in the Kiel classification. The development of monoclonal antibodies and molecular cytogenetics has also made it possible to identify T-cell lymphomas more accurately. For example, many of the malignant lymphomas that were previously considered to be unclas­ sifiable can now be included in a classification scheme that places the T-cell lymphomas alongside of the list of B-cell lymphomas. In 1988 the European Lymphoma Club published an "updated Kiel classification" (STANSFELD et al. 1988) based on this new knowledge. It includes a number of previously undefined types of T-cell lymphoma. Studies done in Japan (T. SUCH! et al.) and China (L. Y Tu) have contributed to the understanding of these lymphoma types.

The blood basophils lead a shadowy existence in the field of hematology, even now, 100 years after their discovery by PAUL EHRLICH. In clinical medicine they were hardly noticed for many decades, since they occur in such small numbers in the blood that small and moderate variations in the basophil count were not detectable with common count­ ing methods. This situation has changed since the in­ troduction of direct counting methods. It was noticed, for example, that the blood basophil count is increased in hy­ perlipemia. In the field of pathology the blood basophil was prac­ tically overlooked until recently. This was due to the fact that with common fixations in aqueous solutions the granules dissolve, so that the cells can no longer be stained specifically and therefore escape observation. This problem was solved through special fixing solu­ tions. However, interest in the blood basophils remain­ ed confined to only a few research groups.