Recent studies indicated that the formation of a major constituent of Alzheimer's disease (AD) senile plaques, called BACpeptide, does not result from normal processing of its precursor, amyloid precursor protein (APP). Since protcolytic cleavage of APP inside its /?A4 sequence was found to be part of APP processing the formation of the PA4-peptide seems to be prevented under normal conditions. We considered whether in AD one of the endogenous proteinase inhibitors might interfere with APP proce s mg. After we had recently found that cultured human ncuronal cells s' synthesize the most potent of the known human proteinase inhibitors, a-t-macroglobulin (arZM), upon stimulation with the inflammatory mediator interleukin-6 (IL-6) we now investigated whether or2M and IL-6 could be detected in AD brains. Here we report that AD cortical senile plaques display strong u2M and IL-6 immunoreactivity while no such immunoreactivity was found in age-matched control brains. Strong perinuclear KIM immunoreactivity in hippocampal CA1 neurons of Alzheimer's discasc brains indicates that neuronal cells are the site of ~t2M synthesis in AD brains. We did not detect elevated IL-6 or or2M levels in the cerebrospinal fluid of AD patients. Our data indicate that a sequence of immunological events which seem to be restricted to the local cortical environment is part of AD pathology.

Human C‐reactive protein (CRP) is the major acute phase reactant during acute inflammation. The human CRP promoter is expressed in an inducible and cell‐specific manner when linked to the bacterial CAT gene and transfected into human hepatoma cell cultures. In this paper we analyze the effect of several recombinant cytokines or CRP promoter inducibility in human Hep3B cells. When cytokines are tested singly the major inducer of CRP‐CAT fusions is interleukin‐6 (IL‐6). Maximal CAT gene expression, however, is only achieved when both interleukin‐1 beta (IL‐1 beta) and IL‐6 are present. The response to the two cytokines is cooperative. Cooperativity is maintained when the CRP promoter is linked to a different coding region, that of the bacterial neomycin phosphotransferase II gene. With a series of 5′ and 3′ deletions we show the existence of two distinct and independent regions responsive to IL‐6 and located upstream to the TATA box. The IL‐1 effect is exerted at the level of downstream sequences that are probably important for optimal mRNA translatability or nuclear‐cytoplasmic transport. Inducibility is not influenced by the activation of protein kinases C or A and does not require new protein synthesis.

There is increasing evidence that neurotrophins, including nerve growth factor (NGF), exert specific effects on cells of the immune system in addition to their neurotrophic actions. This report shows that human monocytes express the trk protooncogene, encoding the signal-transducing receptor unit for NGF. This receptor is functional, since interaction of NGF with monocytes triggered a respiratory burst, the major component of monocyte cytotoxic activity.Durig in vitro differentiation of human blood monocytes to macrophages trk expression decreased, suggesting a maturation-dependent trk regulation. Treatment of monocytes with Staphylococcus aureus Cowan I, a potent activator of monocytes, stimulated trk mRNA synthesis in a time-dependent way, implying a modulatory role for NGF in immune functions. The finding that dibutyryl cAMP elicited a time-dependent trk induction in monocytes as well as in phorbol ester-differentiated promonocytic U937 cells indicates that adenylate cyclase is involved in monocytic trk regulation. These results suggest that NGF, in addition to its neurotrophic function, is an immunoregulatory cytokine acting on monocytes.Nerve growth factor (NGF) is the best characterized of the neurotrophins and regulates the development, differentiation, and functional maintenance of both peripheral and central neurons (1, 2). There is increasing evidence that NGF also exerts specific effects on immune functions. NGF induces shape changes in platelets (3), enhances vascular permeability in rat skin (4), and causes degranulation of rat peritoneal mast cells (5-7), suggesting that NGF is involved in acute inflammatory responses. Furthermore, in humans, NGF promotes colony growth and differentiation of myeloid progenitor cells (8), induces lymphocyte proliferation of both B-and T-cell populations (9), and modulates the formation of lipid mediators by mature basophils (10).The multiple effects of NGF on target cells are directly dependent on initial binding of NGF to specific cell surface receptors. Two classes of NGF receptors can be differentiated by their relative affinities: a major class of low-affinity NGF receptors (LNGFR), possessing a Kd of 10-9 M, and relatively small numbers ofhigh-affinity NGF receptors, with a Kd of 10-11 M (11, 12). High-affinity NGF receptors are known to transduce functional responses to NGF (13). Recent studies have established that the trk protooncogene product, a transmembrane tyrosine kinase, is a receptor for NGF (14) and is phosphorylated on tyrosine after binding its ligand (15,16 MATERIALS AND METHODS Cell Cultures. Human peripheral mononuclear cells were isolated from blood on Ficoll-Paque gradients (Pharmacia), and monocytes were separated from lymphocytes by adherence to plastic culture dishes according to Boyum (24). In vitro maturation of monocytes into macrophages was achieved as described (25). In brief, plastic-adherent mononuclear cells were obtained by exposure of the culture dishes to 4°C for 30 min, followed by vigorous rinsing with cold phosphate-b...

Conditioned medium from human monocytes contains a partially characterized hepatocyte-stimulating factor that simultaneously elevates the mRNA levels of the acute-phase protein /3-fibrinogen and decreases albumin mRNA in rat hepatoma cells. We demonstrate that recombinant human B-cell stimulatory factor 2, which is identical to interferon-/?,?/26 kDa protein and interleukin-HPl, exhibits the same activity as hepatocyte-stimulating factor. Furthermore, a specific antibody against B-cell stimulatory factor 2 was able to inhibit hepatocyte-stimulating factor in conditioned medium from human monocytes. Our data show that hepatocyte-stimulating factor and B-cell stimulatory factor 2 are functionally and immunologically related proteins.

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