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glutaraldehyde fixed vibratome sections using antisera raised to rat and human recombinant IL-1/3. Tissue prepared for ultrastructural analysis was developed and fiat-embedded in epoxy resin. Ultrathin sections were cut and examined under transmission microscope. Microglial cells and neurons could be identified ultra- structurally on basis of cell size, morphology of the nucleus and cell-specific cytoplasmic organelles. In mi- croglial cells, irIL-1 was largely confined to the cyto- plasma and was not associated with secretory vesicles, endoplasmic reticulum or Golgi apparatus. This subcel- lular localization is in line with the absence of a signal sequence in the IL-1/3 precursor protein. Interestingly, microglial cells contained large granules that were heavily irIL-l-positive. Also some neurons contained these irIL-l-positive granules located at sites where neurons were embraced by microglia. These data sug- gest that the large granules which are positive for IL-1/3 in neurons originate from microglia via endocy- tosis. This neuronal localization supports the view that IL-1 is implicated in neuronal survival (Brenneman et al. (1992) J. Neurochem. 58, 454-460) and is also suggestive for a role of IL-1 in neuronal protection during endotoxin challenges.

Sharing of ligands and receptors in the neuroendocrine and immune systems

J. Edwin Blalock Department of Physiology and Biophysics, University of Alabama Birmingham, Birmingham, AL, USA

Today there is little doubt that there is bidirectional communication between the immune system and the CNS. A commonality of ligands and receptors would seem to represent the molecular mechanism for such cross-talk. Thus, the immune system is now recognized as a source of neuropeptides and their receptors while cytokines and their receptors are found within the CNS. Furthermore, regardless of the system, the same secondary messenger molecules can be generated as a result of a particular l igand/ receptor interaction. Therefore, discrimination between functional re- sponses would seem in part to reside in how a certain cell type is genetically programmed to respond. In addition, subtle differences in transcriptional regula- tion and post-translational modification of the neu- ropeptides and cytokines may contribute to differential responsivity to the immune and neuroendocrine sys- tems. Physiologically, these findings suggest that the immune system functions as a sensory organ for stimuli not recognized by the CNS. Indeed, immune system initiation of stress responses as well as local antinoci- ception through lymphocyte-derived endorphins sup- port this view. Contrariwise, the association of certain animal models of autoimmune disease with hypothala- mic disorders suggests an immununoregulatory capac-

ity for the CNS. A complete understanding of this circuitry holds great promise for understanding and treating human neuroimmunologic disorders.

Leukocyte interactions with microvascular endothe- lium of the CNS

Ted A. Yednock, Frdddrique Bard, Laura I. Tanner, Heidi C. Homer , Catherine Cannon, Dawn K. Hines, Erich G. Goldbach, Tim F. Pfankuch and Lawrence C. Fritz Athena Neurosciences, South San Francisco, CA, USA

Under pathologic conditions, large numbers of cir- culating leukocytes pass across the blood-brain barrier endothelium to enter the central nervous system. Lym- phocytes and monocytes are the major infiltrating cells during multiple sclerosis and EAE, while neutrophils predominate following head trauma or ischemia. We have established several in vitro systems that allow us to examine interactions of leukocytes with brain en- dothelium: (1) adhesion of lymphocytes and monocytes to inflamed venules exposed in sections of EAE brain; (2) adhesion of lymphocytes to cultured brain micro- vascular endothelium; and (3) neutrophil adhesion to and transmigration across brain endothelial monolay- ers. We found that the leukocyte adhesion molecule a4/31 integrin plays an important role in the attach- ment of lymphocytes and monocytes to inflamed brain endothelium. Furthermore, in vivo administration of an antibody against a4 integrin effectively prevented ac- cumulation of lymphocytes in the central nervous sys- tem during EAE, as well as the development of paraly- sis. Unlike lymphocytes, neutrophil adhesion to stimu- late brain endothelial cultures was largely inhibited by antibodies against /32 integrin. In addition, anti-/32 integrin prevented the migration of neutrophils across the endothelial monolayer in response to a chemotactic gradient. Thus, as described in other systems, neu- trophils and mononuclear leukocytes preferentially uti- lize different adhesion molecules for interaction with brain endothelium. However, due to the unique barrier function of brain endothelium, specialized leukocyte interactions with brain endothelial cells can be antici- pated.

Regulation of NK cells during acute psychological stress

Roland Jacobs, Manfred Schedlowski, Gertrud Strat- mann, Stefan Richter, Andreas H~ideke, Uwe Tewes, Thomas O.F. Wagner and Reinhold E. Schmidt Department of Clinical Immunoloy, Department of Clin- ical Endocrinology, Department of Medical Psychology, Hannover Medical School, Hannover, Germany

As a model of acute psychological stress, 40 parachutists were examined during their first jump for

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psychological, endocrine, and cellular immunological parameters. In addition to continuous drawing of blood for measuring various hormones, heparinized blood was obtained 2 h prior, immediately after landing, and 1 h after the jump. White blood cell differential counts, phenotype of peripheral blood lymphocytes, activation antigens, natural killer cytotoxicity, antibody-depen- dent cellular cytotoxicity (ADCC), and PHA-induced interleukin 2 production were determined. Distribution of NK and T cells was found significantly changed by psychological stress. A significant (P < 0.001) increase of CD56 ÷ CD16 ÷ NK cells with at least double the absolute numbers was observed. At the same time, an increase of the activation antigens CD2R, CD26 and the p75 interleukin receptor was detected. All parame- ters decreased significantly (P < 0.001) after the jump even compared to baseline values. Correlation analysis with different stress hormones resulted in a significant correlation of NK cell distribution, NK and ADCC activity with noradrenaline secretion. In summary, these data suggest fast changes in distribution of NK cells during psychological stress.

Supported by the Volkswagenstiftung.

The cryptic self and autoimmune disease

K. Moudgil, V. Bhardwaj, V. Kumar, P. Lehmann and E. Sercarz Department of Microbiology & Molecular Genetics, UCLA, Los Angeles, CA, USA

Through a combination of availability and affinity for the MHC, dominant determinants are efficiently presented to the immune system; the other, subdomi- nant and cryptic T cell determinants on the antigen, fail to impact as strongly on the immune system. This is a general feature of the immune system, true for for- eign antigens such as lysozyme as well as self-antigens such as MHC or myelin basic protein. Thus, on self molecules, the set of poorly processed and presented cryptic determinants, which usually amount to at least half of the potential determinants, fail to induce toler- ance, thereby leaving a group of potentially dangerous autoreactive T ceils untolerized. These 'cryptic self' determinants can be presented more efficiently in in- flammatory sites following upregulation of MHC den- sity and the processing machinery. We have recently determined the complete set of potential determinants for the BI0.PL, SJL and their F1, and as expected, the cryptic determinants are in the great majority. In an effort to understand the role of the cryptic self in affecting the expressed T cell repertoire, we have also studied mouse lysozyme (ML) cryptic determinants and their relationship to the anti-HEL (hen lysozyme) pro- liferative T cell repertoire. Strikingly, with few excep- tions, the detailed repertoire elicited by HEL injection

coincides perfectly with the map of cryptic determi- nants on ML, despite the vast differences between the two proteins. In this sense, the cryptic self is not only important with regard to potential autoimmunity, but also in influencing the specificity of the response to related, foreign antigens.

Supported by grants from the MS Society and the NIH.

Presentation of TCR-idiopeptides in the priming of CD4 +, class II-restricted regulatory T cells in EAE

Vipin Kumar and Eli Sercarz Department of Microbiology and Molecular Genetics, University of California, Los Angeles, CA, USA

Most of the encephalitogenic CD4 + T cells in B10.PL mice recognize MBP Acl-9 and predominantly utilize the TCR V/38.2 gene segment, the most preva- lent V/3 gene family in the mature peripheral T cell repertoire. These effector T cells lead to (1) demyeli- nation and (2) ultimately induce their own regulation. We have asked how the downregulation of these effec- tors comes about and if it has any role in the recovery phase of the disease. There is evidence for three differ- ent cells that could communicate in the regulatory circuitry: a CD4 + regulator, a CD8 + suppressor and an antigen-presenting cell. T cells recognizing the C- terminal region of the V/38.2 chain (not CDR III) are activated in mice recovering from EAE. We have gen- erated cloned T cells reactive to the regulatory TCR- idiopeptide and studied their properties. They are re- stricted by I-A v and express CD4 on their surface. When transferred adoptively, these cells are able to down-regulate Acl-9 responses and can protect mice from EAE, but effectively in the presence of CD8 + T cell (Tsup). The CD4 + regulatory T cells (Treg) also utilize a very limited number of TCR V/3 gene seg- ments (predominantly V/314). How is the CD4 + Treg activated? Which APC presents the TCR-idiopeptides in the context of the MHC class II molecule? Prelimi- nary evidence suggests that during induction of EAE, anti-TCR-V/3-chain antibodies are produced, and it may be that these TCR-specific B cells are responsible for presentation of the TCR peptide to the CD4 + Treg.

Supported by NIH Al-28419.

Neurotransmitter induction of glial cell cytokines

J.W. Merrill, F.C. Martin, A.C. Charles, P.A. Anton and F. Shanahan Department of Neurology, UCLA, Reed Neurol. Res. Ctr., Los Angeles, CA, USA

Substance P (SP) is a central and peripheral neuro- transmitter which has been associated with gliotic as-