Spatial and molecular organization of lymph node T cell cortex: a labyrinthine cavity bounded by an epithelium-like monolayer of fibroblastic reticular cells anchored to basement membrane-like extracellular matrix.

Naive T cells encounter antigen-presenting cells within the cortex of lymph nodes to initiate primary immune responses. Within this T cell cortex is the reticular network (RN)--a system of collagen fibers and extracellular matrix (ECM) wrapped by fibroblastic reticular cells (FRC). We have investigated the distribution of various molecules, including ECM proteins and proteoglycans, in the T cell cortex of both human and rodent lymph node. We confirm and extend reports of matrix elements in the RN. In addition, we find that staining for the laminin-alpha3 chain and for tenascin reveals a 'hollow' reticular pattern, consistent with localization to the basement membrane-like covering of reticular fibers. In contrast, keratan sulfate is observed in a fine linear pattern within the RN, suggesting it is localized to the core of the fibers. Staining with the marker ER-TR7 indicates that FRC cover all identifiable ECM surfaces of the T cell cortex. Based on these findings and previous reports, we conclude that cortical lymphocytes migrate within a 'labyrinthine cavity' free of fibrillar ECM, distinguishing the T cell cortex from other loose connective tissues, and that the FRC lining of the cavity constitutes an epithelium-like boundary. We propose that this spatial organization facilitates ameboid leukocyte crawling along preformed paths of least resistance and that the basement membrane-like ECM of the FRC may facilitate fluid transport within the RN by limiting leakage from the fiber.

Reticulum cell neoplasms of lymph nodes: a clinicopathologic study of 11 cases with recognition of a new subtype derived from fibroblastic reticular cells.

Lymph nodes contain nonlymphoid accessory cells including follicular dendritic cells (FDCs), interdigitating dendritic cells (IDCs) and fibroblastic reticular cells (FBRCs). Neoplasms derived from FDCs are uncommon, and those of IDC origin are even more rare. We report the clinicopathologic features of 11 reticulum cell neoplasms, including 2 of FBRC origin. There were seven male patients and four female patients ranging in age from 13 to 73 years. All cases involved lymph nodes (cervical or supraclavicular-6 cases), (abdominal--2 cases), epitrochlear (1 case); two had more than one site of involvement (cervical lymph node and mediastinum--1 case, cervical and abdominal lymph nodes--1 case). One case of FDC tumor had concomitant Castleman's disease, plasma cell variant. Each neoplasm showed similar histology with oval-to-spindle-shaped cells in a storiform or fascicular pattern. Based on immunophenotypic findings, the neoplasms were classified as FDC (five cases), IDC (two cases), FBRC (three cases), and reticulum cell neoplasm, not otherwise specified (one case). The FDC tumors showed immunoreactivity for CD21 or CD35, vimentin, and CD68. The IDC tumors showed strong positivity for S-100 protein and variable positivity for CD68 and CD1a. The cases derived from FBRCs were positive for vimentin, desmin, and smooth-muscle actin. The neoplasm classified as reticulum cell neoplasm, not otherwise specified had similar morphologic features but showed only equivocal positivity for CD68 and vimentin. Follow-up was available for 9 of 11 (82%) cases with a mean of 3.5 years. Four of five patients with FDC tumors were alive with disease when last seen; the fifth is alive and well with no evidence of disease at 4-year follow-up. One patient with IDC tumor had a recurrence in a different nodal site. Two patients with FBRC tumor were disease free at follow-up of 2 years and 8 years, respectively. The patient with reticulum cell neoplasm, not otherwise specified, was alive and disease free 8 years after diagnosis.

Primary low-grade B-cell lymphoma of the dura: a mucosa associated lymphoid tissue-type lymphoma.

The clinicopathologic findings in five patients with primary low-grade B-cell lymphoma of the intracranial dura are described. All patients were women, 40-62 years of age, who presented with focal neurologic symptoms. Radiologic studies showed a well-localized dural mass in each case, raising a preoperative diagnosis of meningioma. Cytologically these were composed of a diffuse infiltrate of small lymphocytes with plasmacytoid differentiation, with a variable admixture of centrocytelike cells. Lambda light chain restriction was found in three cases, and kappa light chain in one. VJ polymerase chain reaction for immunoglobulin heavy-chain rearrangement was positive in three of four cases, including one case in which immunostaining results were equivocal. Staging procedures did not show involvement at any other site. Therapy consisted of radiation (n = 3), chemotherapy (n = 1), or both (n = 1), with excellent response. There was no evidence of recurrence or subsequent dissemination at follow-up of up to 63 months. Low-grade B-cell lymphomas arising in the intracranial dura are rare but appear to be similar to other low-grade B-cell lymphomas arising in extranodal sites in terms of clinical presentation as stage 1E disease, indolent behavior, and favorable response to treatment, suggesting that they may be part of the mucosa associated lymphoid tissue (MALT) lymphoma spectrum. They appear to arise at dural sites where meningothelial cells are concentrated.

Sophisticated strategies for information encounter in the lymph node: the reticular network as a conduit of soluble information and a highway for cell traffic.

The lymph node is the crossroad in which soluble signals and cells carried by lymph meet lymphocytes emigrating from blood. Efficient interactions among these elements depend on the reticular network, which comprises reticular fibers, related extracellular matrix components, and associated fibroblastic reticular cells. This network provides a three-dimensional scaffold for attachment of APCs and pathways for the migration of T cells to these APCs. In addition, the network constitutes a miniature conduit system for bulk flow delivery of soluble molecules to distinct sites in the paracortex, particularly the high endothelial venule. The delivered mediators, such as chemokines, regulate the phenotype of the high endothelial venule, the recruitment of lymphocytes, and the behavior of the recruited lymphocytes. Thus, the reticular network is a multifunctional infrastructure that facilitates encounters of cells with other cells and factors necessary for effective and efficient immune surveillance.

The effects of growth hormone and insulin-like growth factor I on the immune system of aged female monkeys.

The aging process is associated with a significant reduction in circulating GH and insulin-like growth factor I (IGF-I) levels. During this period, immune function also declines. Rodent data suggest that treatment with recombinant human GH (rhGH) or rhIGF-I enhances immune function in normal adult mice. To determine whether rhGH and/or rhIGF-I treatment could improve immune function in aged female rhesus monkeys, we administered rhIGF-I (120 micrograms/kg x day), rhGH (100 micrograms/kg x day), a combination of therapies, or excipient alone by sc infusion using Alzet pumps over a 7-week period. At 28 days, the pumps were replaced, and the animals were bled and immunized with tetanus toxoid. At the end of the 7-week period, the animals were killed. rhGH and rhIGF-I increased serum GH and IGF-I levels, respectively; rhGH and rhIGF-I in combination induced the highest serum IGF-I levels (906 +/- 261 ng/ml vs. control, 185 +/- 36 ng/ml at death). rhGH and rhIGF-I also increased IGFBP-3 levels. rhGH infusion resulted in the most marked changes in lymph node and splenic reactivity, as determined by histological assessment. Lymph nodes from the rhGH-treated animals showed changes from baseline indicating a stimulated reactive state. Both rhGH and rhIGF-I had effects on lymphocyte phenotype, but there were different responses in blood compared to spleen and lymph nodes. In the peripheral blood, the percent B cells and percent CD8 cell count rose after rhIGF-I therapy, with a fall in the CD4/CD8 ratio. In the spleen, on the other hand, the CD4/CD8 ratio nearly doubled (0.33 +/- 0.12 vs. 0.53 +/ 0.12) after rhIGF- I therapy. In the spleen, the combination of rhGH and rhIGF- I increased the percent T cells from 26.7 +/- 2.3 to 42.4 +/- 4.4 and the CD4/CD8 ration to 0.71 +/- 0.11. Both rhGH and rhIGF-I increased in vivo (antibody titer to tetanus toxoid) responses by lymphocytes, and rhGH increased Con-A- induced DNA synthesis in vitro. These results confirm the rodent data showing that rhGH and rhIGF-I cause beneficial changes in immune function and suggest that further investigation is warranted to assess their therapeutic potential.

Orchestrated information transfer underlying leukocyte endothelial interactions.

The specificity and efficiency of leukocyte binding to endothelial cells (ECs) depends on coordinated information transfer from the underlying tissue to endothelium and from there to the leukocyte. We address three distinct information-transfer points in this system: 1, How does the leukocyte read information from the EC? This process is best accounted for by the paradigm of a multi-step adhesion cascade optimized for rapid information readout; it consists of primary adhesion (rolling/tethering), triggering, and strong adhesion. Recent studies with T cells, monocytes, and eosinophils confirm the generality of the paradigm. The concept of primary adhesion has been expanded to involve not only the selectins, but also certain integrins; furthermore, it depends on receptor concentration on leukocyte microvilli. 2. What information from the underlying tissue does the EC transform into signals for the leukocytes? And what rules govern that process? We illustrate the principles with chemokines, believed to participate in the triggering step. The endothelium displays chemokines either (a) directly by "posting" them from other cells or (b) by integrating a variety of tissue and environmental signals and "relaying" that information by producing its own chemokines and surface adhesion molecules. The rules for this endothelial transduction include specificity coupled with redundancy, amplification, synergy, and coordinated induction of ensembles of molecules. Finally, 3. How does the relevant information reach the endothelium? Simple diffusion is sufficient to deliver signals from cells close to the vessel. However, longer range soluble mediator transport appears to be facilitated by fiber bundles, particularly those ensheathed by fibroblastic reticular cells in the lymph node.

Regulation of L-selectin mRNA in Jurkat cells. Opposing influences of calcium- and protein kinase C-dependent signaling pathways.

L-Selectin initiates leukocyte attachment to venular endothelium during lymphocyte recirculation through lymph nodes, leukocyte recruitment into sites of inflammation, and the hematogenous spread of lymphoid malignancies. The density of L-selectin at the cell surface is a major determinant of binding activity and entry into tissues. Post-transcriptional shedding is one control mechanism; however, the extent and physiologic relevance of pre-translational regulation has not been defined. The current study shows that mitogen-/IL-2-driven proliferation of human T cells first increased then markedly decreased the expression of L-selectin on the blast population. The prevalence of specific mRNA showed parallel changes, implying that receptor density is controlled, in part, at the pretranslational level. We used the IL-2-independent Jurkat cell line to determine whether signaling through C-type protein kinases and intracellular calcium regulated L-selectin mRNA directly. Selective pharmacologic activation of these pathways with phorbol esters and calcium ionophore, respectively, resulted in opposite effects on both L-selectin density and mRNA levels. Phorbol esters induced receptor shedding followed by progressive increases in L-selectin density and steady state levels of mRNA. Addition of a calcium ionophore with the phorbol ester blocked both the reexpression of surface receptor and the increase in mRNA. Treatment with ionophore alone resulted in a steady decline in L-selectin expression and mRNA levels. Cyclosporin A, a specific inhibitor of calcineurin, blocked the impact of ionophore on both basal and phorbol-induced levels of L-selectin mRNA. Ionophore alone did not induce apoptosis, significantly alter cell cycle kinetics, or increase transcription of the IL-2 gene under conditions that suppressed L-selectin. Thus, calcineurin seems to be a proximal enzyme in a novel regulatory cascade that suppresses L-selectin expression independent of its known effects on proliferating T cells. In light of the findings in Jurkat, we propose that the protein kinase pathway up-regulates L-selectin mRNA and surface expression early in mitogen-driven T cell proliferation. Chronic elevation of intracellular calcium in repeatedly stimulated T cells then down-regulates expression at the pretranslational level through prolonged activation of calcineurin.

Immunohistochemical assessment of proliferative activity in adrenocortical neoplasms.

Although many histologic criteria have been utilized to help distinguish benign from malignant adrenocortical tumors, it still may be difficult to assess the biologic potential of a given tumor. We evaluated 19 adenomas and 15 primary carcinomas with the avidin-biotin complex peroxidase method utilizing formalin-fixed, paraffin-embedded tissues with monoclonal antibodies for proliferating cell nuclear antigen (PC10) and Ki-67 (MIB 1) to determine if staining for these antigens could be used to help differentiate benign from malignant adrenocortical neoplasms. We also evaluated whether these markers could be used as prognostic indicators. Labeling indices for both PCNA and Ki-67 were determined by enumerating 1000 tumor cells, and expressed as a percentage of cells with nuclear staining. A PCNA and a Ki-67 score was obtained by the product of the staining intensity (0-3+) and the extent of nuclear staining, expressed as an estimate of the percentage of cells staining. Both PCNA and Ki-67 score and labeling index were correlated with mitotic counts, histologic diagnosis, and clinical outcome. Follow-up period for patients ranged from 4 months to 12 years with a mean of 25 months. Mitotic counts correlated with histologic diagnosis and clinical outcome. Both Ki-67 score and labeling index were significantly higher in malignant than in benign tumors, and correlated with mitotic counts and clinical outcome. There was a strong correlation between Ki-67 score and labeling index, indicating that Ki-67 score may be a more rapid and equally accurate method of estimating proliferative index of a tumor. PCNA score and labeling index did not correlate with histologic diagnosis or clinical outcome.(ABSTRACT TRUNCATED AT 250 WORDS)

Enhancement of lymphocyte proliferation assays by use of serum-free medium.

Fetal bovine serum (FBS)-supplemented cell culture medium has been the standard medium used in assays of murine lymphocyte proliferation. While FBS allows cell growth and viability, it requires screening and contains uncharacterized elements which may yield inconsistent results from batch to batch. It also may include growth factors and immunologically reactive proteins that obscure assays for specific responses because of high background proliferation. Recently, chemically defined serum-free media have become available for human lymphocyte culture. We compared several of these media against FBS-supplemented medium and found that one of them, AIM V (Gibco), produced a marked increase in the ratio of positive to background counts in [3H]thymidine incorporation assays of antigen-specific proliferation. Similar results were obtained when responses to mitogenic lectins were examined. AIM V supported proliferation of lymphocytes in a variety of haplotypes, it supported MHC-specific proliferation in response to soluble antigens in a manner consistent with previous reports, and it supported proliferation in response to alloantigen as displayed in the mixed lymphocyte culture. A high ratio of positive to background counts was consistently observed. The results indicate that this serum-free medium enhances the analytic power of proliferation assays.