The regulatory role of macrophages in antigenic stimulation. Part Two: symbiotic relationship between lymphocytes and macrophages

Human mononuclear cells and neutral proteinases. III. Neutral proteinases and rheumatoid arthritis: monocytes as a source of cathepsin G and proteinase potentiation of IgM rheumatoid factor elaboration

We have been interested in contributions of certain cells and mediators to synovial inflammation rheumatoid arthritis (RA). The present studies were designed to determine (1) whether monocytes contained the neutral proteinase cathepsin G and (2) if neutral proteinase could induce or potentiate cellular IgM rheumatoid factor (RF) production. Monocyte-rich and monocyte-poor populations were isolated by Ficoll-Hypaque density sedimentation followed by glass adherence, and cellular lysates were obtained by repetitive freezing and thawing as we have reported for neutrophil-derived neutral proteinase. Cathepsin G was quantified immunochemically by an enzyme-linked immunoassay (ELISA) we developed utilizing commercially available anti-cathepsin G antibodies. Mononuclear and B-cell-enriched cell cultures were prepared by standard methods and IgM RF measured by our ELISA. Cell-derived lysates from monocyte-enriched populations (84 +/- 3% monocytes, less than 1% neutrophils) contained considerably greater amounts of measurable cathepsin G (OD280 = 0.393 +/- 0.153) than lysates from equal numbers of monocyte (15 +/- 2% monocytes, less than 1% neutrophils)-depleted cells (OD280 = 0.071 +/- 0.038; P less than 0.05). Eighteen patients with RA and three normal individuals did not have consistently increased cellular elaboration of Ig or IgM RF in vitro in response to proteinase (trypsin) stimulation; however, patients manifested 80% potentiation by trypsin of pokeweed-stimulated cellular IgM RF production in vitro (pokeweed-stimulated IgM RF 137 +/- 53 ng/ml, pokeweed/trypsin-induced IgM RF 246 +/- 100 ng/ml; P less than 0.02), changes being most striking for those patients seropositive by latex fixation test (84% increase, P less than 0.02).(ABSTRACT TRUNCATED AT 250 WORDS)

Conjunctival epithelial cells infected with Chlamydia trachomatis express HLA-DR antigens

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Decreased expression of HLA-DR antigens on monocytes in patients with multiple sclerosis

Immunofluorescence, cell binding assays and enzyme immunoassays were used to investigate the expression of class II major histocompatibility antigens on peripheral blood monocytes in 67 patients with multiple sclerosis. Monocytes from patients with active disease expressed fewer HLA-DR molecules on their surface than normal monocytes; furthermore the percentage of cells which exhibited detectable amounts of surface HLA-DR antigens was decreased in patients with active multiple sclerosis. During the inactive stage of the disease both deficiencies were milder, probably representing secondary pathogenetic phenomena. Quantitation of monocyte surface HLA-DR antigen expression could be valuable in assessing the clinical disease activity. The demonstration of a molecular defect in patients with multiple sclerosis will improve our understanding of the pathogenesis of the disease.

Prostaglandin and thromboxane in liposomes: suppression of the primary immune response to liposomal antigens

Liposomes containing lipid A as adjuvant and also containing prostaglandin E2 or thromboxane B2 were examined for the ability to influence induction of humoral immunity against liposomal protein or lipid antigens in rabbits. The protein antigen consisted of cholera toxin that was bound to ganglioside GM1 on the surface of the liposomes. High titers of anti-cholera toxin antibodies were produced and IgM and IgG responses were detected. When the immunizing liposomes contained either prostaglandin E2 or thromboxane B2 as part of the lipid bilayer, the primary immune response, involving both IgM and IgG antibodies, was greatly reduced. The secondary immune response observed after a boosting immunization was not suppressed by liposomal eicosanoids. A similar inhibitory effect on the primary response was observed when liposomal lipid antigens were examined instead of cholera toxin. An inhibitory effect of liposomal prostaglandin E2 on the phagocytic uptake of opsonized liposomes by cultured macrophages was also observed, suggesting that liposomal eicosanoids can have direct local effects on macrophages that might influence the immune response to liposomal antigens.

Immunopathology of trachomatous conjunctivitis

Upper palpebral conjunctival biopsy specimens obtained from eight patients with active trachoma were examined by routine histological and immunohistochemical methods. The epithelium expressed class I major histocompatibility complex (MHC) products throughout and class II MHC products in the superficial layers. The epithelial inflammatory infiltrate consisted of polymorphonuclear leucocytes, macrophages, T lymphocytes, and dendritic cells. In the underlying stroma the inflammatory infiltrate was organised as B lymphoid follicles, and there was also a diffuse infiltrate consisting of plasma cells and scattered B lymphoid cells, dendritic cells, T cells, macrophages, and polymorphonuclear leucocytes. Each type of cell has its special location in the tissue. Plasma cells were located on a subepithelial band and as a dense infiltrate round the acini of accessory lacrimal glands. IgA+ plasma cells outnumbered IgG+ cells, whereas IgM+ and IgE+ cells were few. Our data provide good evidence for the presence of both humoral and cell mediated immune responses and a possible role for autoimmune mechanisms in the conjunctival tissues of trachoma patients.

1,25-Dihydroxyvitamin D3 (calcitriol) suppresses concanavalin A-stimulated human T cell proliferation through monocytes

1,25-Dihydroxyvitamin D3 (calcitriol) inhibits mitogen-stimulated T cell proliferation by blocking the production of interleukin 2 (IL-2). The present study was initiated to determine the role of monocytes (Mo) in this process. Either Mo or T cells were preincubated with calcitriol for 24 or 48 hr and were thoroughly washed prior to concanavalin A (Con A)-stimulated coculture period. The inhibitory effect of calcitriol was Mo mediated; pretreatment of Mo resulted in inhibition of T cell proliferation, whereas pretreatment of T cells lacked the suppressive effect. Similar results were obtained by using 7- to 20-day-old IL-2-dependent human cultured T cells instead of fresh T cells. Calcitriol did not diminish the IL-1 secretion or intracellular IL-1 production of fresh Mo and actually increased the secretion of 24-hr-old Mo. Furthermore, addition of recombinant IL-1 to Mo-T cell coculture failed to reconstitute proliferative defect. Thus, these experiments clearly demonstrate that the suppression of Con A-driven T cell proliferation by calcitriol is Mo mediated and works by a non-IL-1 mechanism. At least, under these experimental conditions of Con A-driven T cell proliferation in which Mo play an obligatory role, antiproliferative action of calcitriol is Mo dependent.

Immune cells in a case of postherpetic marginal trophic ulcer

The corneal surface was examined by means of replica histology, and the excised limbic conjunctiva was examined by routine histological and immunohistochemical methods with monoclonal antibodies directed against major histocompatibility class II antigens, lymphocyte subsets, Langerhans cells (HLA-DR, OKT4-Leu3a, OKT8, BA1, B1, and OKT6) and immunoglobulins A, G, M, and D. The findings were compared with those found in normal conjunctiva. No inflammatory cells were present in the replica of the corneal surface. An inflammatory infiltrate composed of B lymphocytes and null cells, in addition to T lymphocytes, Langerhans cells, and polymorphs, was present in the epithelium as well as in the stroma of the limbic conjunctiva. The composition of the infiltrate points towards the involvement of cell mediated immunity as well as humoral immunity. No immunoglobulins were bound to the conjunctival epithelium.

The in vitro proliferative response of lymphoid cells of mice infected with Salmonella enteritidis 11RX

Intraperitoneal injection of (BALB/c x C57BL/6) F1 mice with live, but not killed Salmonella enteritidis 11RX (11RX) induced T cells in the spleen and peritoneal cavity which were able to proliferate in vitro in response to two different forms of 11RX antigens. The majority of cells which proliferated were L3T4+ T cells and most of the response was restricted by the I-A locus of the H-2 major histocompatibility complex, although a smaller K region restricted response was also detected. T cells able to respond to 11RX antigens could only be demonstrated when non-adherent lymphoid cell suspensions from immunized mice were used, and usually a limited response was obtained unless small numbers of adherent cells present in normal peritoneal cell suspensions were added. Cells cultured in vitro for 3 days were able to mediate local transfer of delayed type hypersensitivity and secondary immunization did not enhance the reactivity of responding cells to 11RX antigens.

Changes in macrophage populations: phenotypic differences between normal and tumor-bearing host macrophages

As a tumor grows, changes occur in the function of macrophages (M phi). This is concomitant with changes in their phenotype. Flow cytometric analysis of monoclonal antibody (mAb)-labeled thioglycollate-elicited peritoneal, and resident splenic, M phi showed a tumor-induced shift of Mac-1, -2, -3, and Ia antigen expression. During tumor growth, the percentage of peritoneal Mac-2+, -3+, and Ia+ M phi decreased significantly (22%, 14%, and 58%, respectively), while Mac-1+ M phi remained unchanged. By analyzing the data on two-dimensional histograms and comparing the sizes of M phi to cell-surface antigen expression, we identified distinct subpopulations of peritoneal M phi. Three distinct size versus antigen expression M phi subpopulations were detected by flow cytometry and consisted of 10-16, 17-22, and 23-27 microns for the small-, medium-, and large-sized populations, respectively. Large-sized Mac-1+ and -2+ M phi decreased (37% and 38%), while large-sized Mac-3+ M phi did not decrease during tumor growth. Medium-sized Mac-3+ M phi decreased 33% during tumor growth, while no differences could be seen in medium-sized Mac-1+ or -2+ M phi. Concomitant with the decrease in large-sized Mac-1+ M phi was an increase in small-sized Mac-1+ M phi. Peritoneal Ia+ M phi were mostly small-sized (4-7-fold increase over the medium-sized and none in the large-sized population). M phi Ia antigen expression was nearly absent in the 21-day tumor-bearing host, with less than 4% of the cells labeling positive (a 73% drop from normal host M phi). In splenic M phi, the percentage of Mac-1+ M phi significantly increased (90%) during tumor growth, while Mac-2+ and -3+ M phi showed a smaller, but still significant, increase (48% and 40%, respectively). Additionally, splenic Ia+ M phi significantly decreased (29%) during tumor growth. More important than the decreased cell numbers was the significant decrease in Ia antigen expression per cell. Unlike the peritoneal M phi, the splenic M phi did not show distinct size versus antigen expression subpopulations, although there was an overall difference in M phi size between normal and TBH. These data suggested that M phi from different anatomical sites are phenotypically different and tumor growth mediates phenotypic alterations in peritoneal and splenic M phi populations. This may be the source of tumor-induced dysfunction of M phi-mediated immune activity.

Delta-9-tetrahydrocannabinol inhibits macrophage protein expression in response to bacterial immunomodulators

The objective of this study was to determine the effect of delta-9-tetrahydrocannabinol (delta-9-THC), the major psychoactive component of marihuana, on macrophage protein expression in response to bacterial immunomodulators. Peritoneal macrophages of (B6C3)F1 mice receiving Propionibacterium acnes exhibited a novel protein profile when compared to resident or vehicle-treated macrophages. In contrast, macrophages from mice treated with P. acnes in concert with delta-9-THC exhibited profiles for which the majority of protein species reverted to patterns seen in profiles of resident or vehicle-treated macrophages. Treatment of the murine macrophage line P388D1 (DBA/2) in vitro with bacterial lipopolysaccharide (LPS) resulted in the hyperproduction of a subset of proteins ranging from 73 to 18 kD relative molecular weight. Coexposure of the P388D1 cells to LPS and 10(-7) M to 10(-5) M delta-9-THC resulted in a dose-related depletion of these proteins. These results suggest that delta-9-THC suppresses the expression of proteins elicited by macrophage bacterial immunomodulators.

Tumor-induced variations in a high molecular weight inhibitory monokine

A soluble inhibitor of T cell proliferation was demonstrated in splenic and peritoneal macrophage (M phi) culture supernatants and was variably glycosylated during tumor development. This factor(s) inhibited mixed lymphocyte reaction- (MLR) and concanavalin A-induced T cell proliferation and was not prostaglandin E2 (PGE2), as demonstrated by size (nondialyzable, found in a 30 kilodalton [kd] ultrafiltration retentate and in fractions corresponding to greater than 67 kd on S-200 Sephacryl chromatography) and time course of activity in the MLR. Concentrated supernatants were PGE2-free and yet inhibited proliferation in the MLR. Isoelectric focusing (IEF) revealed normal and tumor-bearing host (TBH) concentrated M phi supernatants' major peaks of inhibitory activity differed in charge, with a pI of 6.5-7.6 for normal hosts and 4.0-6.0 for TBH. Activity in TBH M phi supernatants was found primarily in fractions eluting from hydroxylapatite at 0.3 M sodium phosphate buffer, pH 7.3, was resistant to proteolytic enzymes, but was sensitive to neuraminidase. In contrast, inhibitory activity in normal host M phi supernatants eluted from hydroxylapatite at 0.6 M sodium phosphate buffer and was not sensitive to neuraminidase. Thus, variable glycosylation (presence and absence of sialic residues) could account for the charge difference seen in IEF and may have a bearing on tumor-induced hyporesponsiveness. Kinetic addition of supernatants to the MLR revealed PGE2 may be required for inhibitory activity to be manifested early (0 and 24 h) but not if the high molecular weight (mw) inhibitor was added late (48 and 72 h post initiation). Both normal and TBH M phi supernatants suppressed the generation of interleukin 2 (IL 2) with a dose- and time-dependent difference. Cell-cycle analysis of mitogen-stimulated cells treated with normal and TBH M phi supernatants revealed that TBH M phi supernatants enhanced cell-cycle progression when measured early, but that both normal and TBH M phi supernatants suppressed the number of cells in S phase when measured late in the assay. The production of a high mw inhibitor by both normal and TBH M phi could suggest a homeostatic mechanism, which was upset by increased PGE2 production and production of an inhibitor containing sialic acid, tipping the balance in favor of immunosuppression.

Immunogenic capacity of macrophage hybridomas

Two clones, E2-7.7 and E2-10.50, derived from two macrophage(M phi)hybridomas, E2-7 and E2-10, have been studied. The first clone, E2-7.7, is Ia+ and Fc receptor (FcR) negative and manifests a strong antigen-presenting capacity. When we pulsed its cells in vitro with keyhole limpet hemocyanin (KLH) antigen and injected them into syngeneic animals, we found that as small a dose as 10(3) cells initiated an immune response in vivo. On the other hand, antigen-pulsed cells of the E2-10.50 clone, which are Ia- and FcR+, were almost incapable of triggering immunity, even when injected at a dose of 10(5) cells. Thus, the two clones differ in their immunogenic capacity (both cellular and humoral immunity). In experiments aimed at testing the stimulation in vitro of primed lymph node (LN) cells by antigen-pulsed cells of these two hybridoma clones, we observed that E2-7.7 stimulated the unfractionated population of LN cells and the LN-derived population of T cells. The E2-10.50 cells stimulated only the unfractionated population of LN cells, but not the T cell population. Subsequent tests indicated that the E2-10.50 cells require an intermediate Ia+ accessory cell to present the antigen to the T lymphocytes. Analyzing the molecular structure of the M phi hybridomas, we discovered that major histocompatibility complex (MHC) genes of the myeloma haplotype (H-2d), and of the splenic M phi used for fusion (H-2k), which were not expressed in the parental myeloma or in the E2-10.50, were expressed in the E2-7.7. Thus, somatic cell fusion of M phi resulted in the activation of suppressed genes of the myeloma partner. It appears that these antigens participate in controlling the immunogenic properties of the E2-7.7 clone. Testing the effects of interferons on the M phi hybridomas, we observed that interferon-gamma activated, at both the mRNA and the cell surface-antigen levels, the expression of H-2Dk, H-2Kd and H-2Dd in the E2-10.50 cells, but not in the E2-7.7. Consequently, interferon-gamma augmented significantly antigen presentation by E2-10.50 but not by E2-7.7 cells. These two hybridoma clones might represent two distinct subsets of normal M phi, manifesting two different sets of functional properties.(ABSTRACT TRUNCATED AT 400 WORDS)

Histological and ultrastructural study of the inflammation evoked by Paracoccidioides brasiliensis antigen in previously immunized mice

Bentonite particles uncoated and coated with soluble antigen of Paracoccidioides brasiliensis (Pb) were intravenously injected into mice with and without previous immunization with Pb antigen. The inflammatory reaction around the bentonite emboli in small lung vessels was quantitated and morphologically studied by light and electron (EM) microscopy, 2 to 8 days after challenge. In control nonimmunized animals, coated and uncoated bentonite particles caused mild and nonspecific inflammation made up by macrophages. By EM, they formed loosely aggregated clusters with cytoplasm containing few organelles and borders without interdigitation. In immunized mice injected with coated bentonite particles, the inflammatory area was significantly greater than that in nonimmunized animals in all periods of study with maximum difference at day 2. The inflammatory process at days 2 and 4 was characterized as mature granulomata, composed of macrophages with great number of organelles in the cytoplasm, large euchromatic nuclei and prominent nucleoli. Altogether these findings indicated a lesion with high metabolic activity, compatible with a granulomatous hypersensitivity reaction. At days 6 and 8, there was a change from mature to epithelioid granulomata, well demonstrated by EM which showed macrophages with characteristically interdigitated cytoplasmic borders. The results strengthen the importance of cellular immunity in the genesis of epithelioid granuloma in paracoccidioidomycosis and reinforce the usefulness of the present model in studies of the inflammatory cellular sequency and events in this mycosis.

Tumor-induced alteration in macrophage accessory cell activity on autoreactive T cells

Using a tumor-model system, differences in the accessory cell capabilities on autoreactive T cells of splenic macrophages from normal and tumor-bearing hosts (TBH) were assessed in the syngeneic mixed lymphocyte reaction. Tumor development caused a drop in autoreactivity. At 0 and 7 days of tumor growth, no drop in reactivity occurred when TBH macrophages were used as accessory cells and L3T4+ autoreactive T cells from normal mice were used as responder cells. However, by day 14, there was a 32% drop in reactivity, and by day 21 only 22% of the T cell reactivity remained when TBH macrophages were used as accessory cells. Alterations in macrophage Ia antigen during tumor growth were first investigated as the potential cause of reduced autoreactivity. Before tumor growth (day 0) 59% of the splenic macrophages were found to be Ia+. Day-7 TBH macrophages showed no difference in Ia antigen expression when compared to day 0 macrophages. However, by day 14, TBH macrophages showed a 9% decrease, and by day 21 they showed a 36% decrease in the number which were Ia+. Concomitant with the decrease in the number of Ia+ cells was a decrease in the density of Ia antigen expression on day-14 and -21 TBH macrophages. In day-14 and -21 TBH macrophages, two populations were seen that were Ia+. The first had a 10%-20% decrease in Ia antigen expression per cell while the second population had a greater than 50% drop in Ia antigen expression per cell. By titrating and mixing TBH macrophages with normal host macrophages, we assessed whether they could actively mediate suppression of autoreactive T cells. A titratable suppressive phenomenon was demonstrated using day-21 TBH macrophages. In contrast, day-7 and -14 TBH macrophages titrated with normal host macrophages had no effect on the syngeneic mixed lymphocyte reactivity. Lastly, we investigated whether the macrophage-mediated suppression was caused by increased prostaglandin secretion. Addition of indomethacin to cultures increased autoreactive T cell reactivity stimulated by normal or TBH macrophages (59% and 99% increase, respectively). Although indomethacin reduced suppression mediated by TBH macrophages, autoreactivity did not return to levels induced by untreated or indomethacin-treated cells from a normal host. Taken together, the data suggested that tumor growth modulates the function of macrophage accessory cells with autoreactive T cells in at least two ways: by decreasing Ia antigen expression and by increasing suppressor activity.

Antigen-presenting cells for unprimed T cells

The triggering requirements of T cells differ for primed and unprimed cells: primed T cells can be triggered to produce lymphokines without viable antigen-presenting cells (APCs), apparently by crosslinking the T-cell receptor (TCR). Unprimed T cells do, however, require viable APCs and here Jonathan Sprent and Mary Schaefer review what type of cells can carry out this function, with particular reference to APCs for unprimed CD8+ cells.

Testing for cell surface forms of class II major histocompatibility complex antigens and Ii by radioiodination, biotinylation, and membrane immunofluorescence

Antibodies to either Ii or class II major histocompatibility complex (MHC) antigens did not recognize cell surface forms of Ii in immunoprecipitates of cells that had been radioiodinated by the lactoperoxidase method, whereas they bound [35S]methionine metabolically labeled molecules. N-hydroxysuccinimidobiotin (NHS-B) and biotin hydrazide (B-H) were used to react more generally with cell surface proteins via amino groups and nitrene coupling, respectively. Each of these latter compounds labeled alpha and beta chains of class II MHC antigens as seen in Western-blotted, electrophoresed immunoprecipitates probed with 125I-labeled streptavidin but not Ii or its associated forms. Although tyrosine residues might have been inaccessible to radioiodination in carbohydrate-derivatized forms of Ii, the lack of Ii biotinylation in these controlled, sensitive studies was consistent with the view that Ii forms were not surface expressed, with the possible exception of the chondroitin sulfate-derivatized forms of Ii (Ii-CS).

Mechanisms of antigen processing

Using MAb and monovalent Fab probes and saponin permeabilization we have demonstrated that PEC and TA3 B lymphoma-hybridoma cells contain a significant intracellular pool of Ia. At least in TA3 cells, this intracellular pool was independent of protein synthesis. In PEC, adherence caused redistribution of Ia with disappearance of the intracellular pool. Endocytosis of Ia occurred in both TA3 and PEC, and internalized Ia reached a plateau level corresponding in size to the total intracellular Ia pool revealed by saponin treatment. These results suggest that intracellular Ia is largely in a recycling pool derived from the plasma membrane by endocytosis. Subcellular fractionation studies suggest that Ia processing occurs in endosomes similar to those involved in transferrin processing. Antigen processing by TA3 cells was found to be unaffected by cycloheximide. In contrast, antigen processing by adherent PEC was markedly inhibited by cycloheximide, despite the fact that they maintained surface Ia and were still capable of presenting antigen peptides. This suggests that an important intracellular Ia processing step or antigen processing step was blocked in these cells. Adherent PEC may contain less recycling Ia, making protein synthesis the major source for intracellular Ia and the availability of intracellular Ia sensitive to cycloheximide. Alternatively, the inhibition of antigen processing by cycloheximide in PEC may reflect depletion of enzymes or other factors involved in antigen processing. Proteins and polysaccharides may interfere with the events that result in the formation of an immunogenic Ia-peptide complex. We had previously documented that peptides compete for the binding site of Ia molecules. We discussed here a second form of interference by polysaccharides and microbial products. These materials did not compete or interfere with the binding and presentation of processed peptides by Ia. Rather, their presence inside the macrophage inhibited MHC-dependent presentation of immunogenic proteins by inhibiting intracellular steps in antigen processing. This intracellular interference with antigen presentation can be of major importance in the presentation of complex mixtures of protein and carbohydrates.

Phenotypic characterization of inflammatory cells in phlyctenular eye disease

Phlyctenular conjunctival biopsy specimens obtained from seven patients presenting with ulcerated limbal phlyctens were examined with routine histology and immunohistochemistry using a panel of monoclonal and polyclonal antibodies and immunoperoxidase techniques. Large numbers of mononuclear phagocytes, dendritic Langerhans cells and polymorphonuclear leukocytes and moderate numbers of T-lymphocytes were observed in the epithelium. This infiltrate was most intense at the basal epithelial layers which expressed HLA-DR antigens. The underlying stromal inflammatory infiltrate was organized as perivascular cuffs and a scattered subepithelial infiltrate, and consisted of many mononuclear cells and poly-morphonuclear leukocytes. Among the mononuclear cells, monocyte derived cells dominated and included monocytes macrophages and dendritic cells. T-lymphocytes were present in moderate numbers, whereas B-lymphocytes and plasma cells, mostly of IgA class, were infrequent. These findings provided in situ immunohistochemical evidence that phlyctenular eye disease is the result of delayed type hypersensitivity immune response in which monocytes and monocyte derived cells play a central role.

Arginine, protein malnutrition, and cancer

The amino acid arginine has anabolic and immunostimulatory properties. This study evaluated the potency of arginine in limiting the severe nutritional and immunological insults of protein calorie malnutrition and increasing tumor load. In protein-depleted A/J mice (n = 340) bearing either an immunogenic (C1300) or poorly immunogenic (TBJ) neuroblastoma, arginine supplementation [1%] significantly augmented T lymphocyte responses (mitogenesis, interleukin-2 production) compared with both a glycine-supplemented and nonsupplemented group. Arginine supplementation significantly retarded the growth of C1300 and prolonged median host survival. These results correlated with augmented autologous mixed lymphocyte tumor cell responses and enhanced specific cytotoxicity. This anti-tumor effect was not demonstrated in mice bearing TBJ where both arginine and glycine stimulated tumor growth compared with nonsupplemented mice. There was no significant difference between arginine and glycine in preservation of carcass weight. These studies suggest that the immunostimulatory effects of arginine are not due to supplemental nitrogen and that an associated antitumor effect is dependent on tumor antigenicity.

Effects of cholera toxin on delayed-type hypersensitivity to sheep red blood cells inoculated intranasally into mice

The effects of cholera toxin (CT) on delayed-type hypersensitivity (DTH) to sheep red blood cells (SRBC) were studied in mice sensitized by intranasal administration of SRBC. CT (1 microgram/mouse), given intranasally together with SRBC (2 x 10(7)/mouse), induced a maximally enhanced DTH response, which reached its peak around 7 days after sensitization, and also induced an accelerated DTH response upon a second administration of SRBC 28 days later. The ability of CT to enhance the DTH to SRBC was lost, either when CT was administered via the intraperitoneal or subcutaneous route, or when CT was introduced into the nasal site from which a large proportion of the SRBC was discharged 2 days after SRBC administration. These results indicate that the cells that are located in the nasal site and participate in the earlier events of DTH response were most affected by CT. The following effects of CT on the earlier events, which occur within 24 hr after the intranasal administration of both CT and SRBC, appeared to be involved in the mechanisms by which CT enhances DTH to SRBC: (i) facilitation of the penetration of the antigen into the nasal tissue; (ii) reinforcement of the migration of immunocompetent cells from the blood to the nasal tissues; (iii) promotion of the ability of Ia-positive macrophages to present the antigenic determinants to T cells; (iv) facilitation of the differentiation of primed T cells to DTH-effector T cells.

Role of the macrophage in the pathogenesis of experimental autoimmune myasthenia gravis

To clarify the role of Ia antigen positive macrophages which invade motor end-plates in the induction of the chronic phase, experimental autoimmune myasthenia gravis (EAMG) rats were injected intraperitoneally with silica dust on day 6 after immunization. Silica injection partially inhibited the invasion of motor end-plates with macrophages as compared with a saline injection. The titer of antibodies to the Narke acetylcholine receptor (AChR) in the chronic phase did not differ in either the saline or the silica groups, while the titer of antibodies to rat-AChR (non-crossreactive antibodies) was lower in the silica group than in the saline group. The silica group survived longer than the saline group. These results suggest that Ia antigen positive macrophages in the acute phase act as antigen-presenting cells and play an important role in the production of antibodies to self-AChR in the chronic phase.

Dendritic cells and macrophages expressing class II antigens in the normal rat incisor pulp

This study has identified and characterized class II (Ia) antigen-expressing cells in the normal rat incisor pulp by immunohistochemistry and flow cytometry. Two types of Ia-expressing cells occurred: one with a pronounced dendritic appearance located primarily in the periphery of the pulp, and one with morphological characteristics similar to those of macrophages. The latter cells were mainly observed in the central portion of the pulp. A numerical ratio of 1:4 was established between the two cell types. The existence of Ia-expressing cells suggests an inherent capacity of the pulp to process and present foreign antigens.

Heterogeneity of human lymphokine (IL-2)-activated killer (LAK) precursors and regulation of their LAK induction by blood monocytes

Highly purified lymphocytes (greater than 99%) and monocytes (greater than 90%) were isolated by CCE from peripheral blood of healthy donors. Blood lymphocytes were separated by this CCE into 9 subpopulations. The NK activities of these lymphocyte fractions against NK-sensitive K-562 cells and their LAK activities against NK cell-resistant target (Daudi) cells were assayed promptly or after incubation of the fractions for 4 days with or without an optimal concentration of IL-2. NK and LAK activities were measured by 4-hr 51Cr-release assay. On the basis of their NK and LAK activities, these lymphocyte fractions were classified into 3 subpopulations of LAK precursors: one lacking both NK and LAK activities (Fr.2), one with moderate NK activity but low LAK activity (Fr.5), and one possessing both NK and LAK activities (Fr.8). Addition of autologous fresh monocytes to the lymphocyte cultures resulted in a significant increase in induction of LAK activity in Fr.2 and Fr.5. This up-regulation of lymphocytes in Fr. 2 and Fr.5 by monocytes was confirmed in parallel experiments by measuring the blastogenic response of the lymphocytes to IL-2. Deletion of lymphocytes in Fr. 8 of CD16+ (Leu-11+) NK cells resulted in 74% reduction in LAK induction, whereas depletion of mixtures of monocytes and lymphocytes in Fr. 2 of cells reacting with CD3+ (OKT3+) antibody resulted in a 66% reduction in LAK induction. This up-regulation of LAK cell induction from LAK precursors by monocytes was confirmed using 4 lines of human lung cancer cells as targets for LAK activity. These results clearly indicate that human monocytes may cause up-regulation of the expression of IL-2-induced LAK activity in T cells and in a subpopulation of NK cells.

Role of Langerhans cells and Thy. 1+ effector cells in herpes simplex virus-1 infection in the skin of newborn mice

Langerhans cells function in the epidermis as very potent accessory cells. Their role as antigen-presenting cells in the immune response following herpes simplex virus type 1 (HSV-1) skin infection of newborn mice was studied. Newborn C 57 BL/6 mice were found to be susceptible while adult mice are resistant to HSV-1 infection in the skin. Because the immune response to HSV-1 infection in the skin is mainly cell-mediated, and therefore dependent on the presence of functional accessory cells, the state of Langerhans cells in the skin of newborns was studied. Staining of whole epidermal mounts revealed similar numbers of Ia+ and ATPase+ Langerhans cells in the epidermis of newborn and adult mice. In a skin lymphocyte reaction assay, Langerhans cells derived from newborn mice were shown to stimulate proliferation of T cells derived from adult allogeneic mice to the same degree as adult-derived Langerhans cells. HSV-1 was injected into the skin of C 57 BL/6 newborn mice together with various preparations of adult-derived spleen cells devoid of antigen-presenting cells. The injected adult-derived lymphocytes were found to confer protection against HSV-1 infection in newborn mice, despite the lack of detectable antigen-presenting cell (APC) function in this cell preparation. The cell subset involved in the transfer of resistance was found to be Ia- and Thy. 1+.

Induction of responsiveness to IL 2 in Con A-stimulated rat lymphoid cells requires synergistic action of IL 1 and the accessory cell membrane

Rat spleen or lymph node cells stimulated with Con A and cultured at a low density of 1 x 10(5) cells per ml proliferated in response to IL 2-containing supernatants and thus expressed receptors for IL 2. Cells depleted of accessory cells either by passage over a glassbead-column or by treatment with the lysosomotropic agent leucine methyl ester (Leu-OMe) did not proliferate in response to IL 2-containing supernatants. The diminished proliferative response after adherent cell depletion could be reconstituted by the addition of peritoneal exudate cells (PEC). Reconstitution could also be achieved by synergistic action of IL 1 and paraformaldehyde-fixed peritoneal exudate cells, indicating an important role for the accessory cell membrane in the induction of IL 2-mediated proliferation.

Anti-Ia antibody diminishes ocular inflammation in experimental autoimmune uveitis

An experimental model of inflammatory eye disease, experimental autoimmune uveitis (EAU), was established by injecting rats in the footpad with S-antigen in complete Freund's adjuvant. This model system was used to evaluate the role of major histocompatibility complex (MHC) class II antigens (Ia) in the pathogenesis of this T cell mediated disease. One day prior to S-antigen priming, rats were injected with either anti-Ia antibodies or with mouse ascites. Clinical and histopathological analysis of eyes from rats treated with anti-Ia antibody showed less ocular inflammation as well as a delay in onset of EAU when compared to controls (p = 0.01). Furthermore, immunocytochemical evaluation demonstrated that tissue obtained from animals receiving anti-Ia therapy also expressed less Ia antigen, as well as a diminution in the number of infiltrating macrophages and lymphocytes. These data show that anti-Ia treatment significantly modifies the course of EAU in the rat. In addition, this study suggests that MHC class II antigen expression may be involved in the initiation and continuation of immune responses that results in ocular inflammatory diseases.

The spleen in Hodgkin's disease. An immunohistochemical study of lymphocyte subpopulations and macrophages

Lymphocyte subpopulations and macrophages in 16 spleens from patients with Hodgkin's disease were analysed immunohistochemically using monoclonal antibodies of the Leu and the Ki M series. In non-involved splenic tissue there is an increase of T-lymphocytes with an increased T-helper/T-suppressor cell ratio, while Ki M-1, -2, -3 and -5-positive, i.e. phenotypically different macrophages, are reduced. These results indicate that involvement of the spleen in Hodgkin's disease is accompanied by changes with respect not only to lymphocyte subpopulations but also to cells of the mononuclear phagocyte system. The immunodeficiency associated with Hodgkin's disease is probably not solely due to lymphocyte dysfunction, since the disease may lead, at least in the spleen, to alterations in macrophages and accessory cells and this may contribute to the impairment of cell-mediated immunity.

Dendritic cells from rat lung are potent accessory cells

Accessory cells are required for the induction of lymphocyte proliferation in response to mitogens or antigens. Rat pulmonary cells were tested for the presence of accessory activity in lymphocyte proliferation induced by sodium periodate. Buffer-perfused lungs were excised, minced, and enzymatically digested. The resulting pulmonary cells (PC) were separated into high density (HD-PC, 32 to 57%) and low density (LD-PC, 9 to 32%) fractions in a discontinuous density gradient of bovine plasma albumin (BPA). Both macrophages and dendritic cells were observed in the LD-PC by light microscopy. HD-PC, LD-PC, adherent LD-PC, nonadherent LD-PC, and a purified preparation of pulmonary dendritic cells (DC-P) were tested for accessory activity in the presence of periodate-treated, lymph-node-derived lymphocytes as responders. Most of the accessory activity was found in the LD-PC. Increasing numbers of LD-PC stimulated proliferation of responder lymphocytes in a linear, dose-dependent manner; higher numbers had a suppressive effect. Nonadherent LD-PC containing dendritic cells also produced a dose-dependent increase in periodate-induced lymphocyte proliferation, whereas adherent LD-PC, morphologically identified as macrophages, were suppressive. Removal of phagocytic macrophages from nonadherent LD-PC resulted in an eightfold increase in both the percent of DC-P present and the amount of accessory activity in the LD-PC. We conclude that pulmonary dendritic cells are potent accessory cells for periodate-induced lymphocyte proliferation.

Kinetics of gamma interferon binding and induction of major histocompatibility complex class II mRNA in Leishmania-infected macrophages

Cells of the monocyte-macrophage series must carry out discrete accessory-cell functions during the process of antigen-specific T-cell activation. One of these functions is the cell-surface expression of major histocompatibility complex (MHC) class II gene products, which are involved in the presentation of foreign antigen to T cells. Previously, we reported that murine peritoneal macrophages infected with the obligate intracellular protozoan Leishmania donovani had suppressed responses to gamma interferon (IFN-gamma) for the induction of MHC class II antigen expression. To determine the molecular basis for this suppression, we examined in the present series of experiments the interaction of this organism with cells of the murine macrophage tumor cell line P388D1. When infected with Leishmania, these cells were also markedly unresponsive to IFN-gamma for the induction of MHC class II antigen expression. This finding was not the result of a defect at the level of the IFN-gamma receptor. Thus, when 125I-labeled IFN-gamma was used, infected macrophages were found to express normal numbers of high-affinity IFN-gamma receptors, and ligand-receptor binding resulted in rapid internalization of labeled IFN-gamma. Despite normal ligand-receptor interactions, the induction in infected cells of mRNA encoding MHC (H-2) class II I-A alpha and beta chains in response to IFN-gamma was markedly suppressed. However, infected cells had normal levels of mRNA encoding the cytoskeletal protein actin. These findings indicate that Leishmania interferes with IFN-gamma induction of macrophage MHC class II antigen expression by down-regulating lymphokine induction of MHC class II mRNA. Suppression of class II expression by this intracellular parasite may prevent subsequent T-cell recognition of infected macrophages and thus favor parasite survival.

Prostaglandin E2 depresses antigen-presenting cell function of peritoneal macrophages

Eicosanoids play a prominent role in trauma. Such mediators of inflammation negatively influence cell-mediated immunity (CMI). There is, however, no information available on the effect of eicosanoids on a critical event in CMI, i.e., antigen-presenting (AP) cell function of macrophages (M luminal diameter), a cellular process responsible for the activation of T and B lymphocytes. The aim of this study, therefore, was to examine the effect of prostaglandin E2 (PGE2) and thromboxane B2 (TXB2) on AP cell function of the peritoneal M luminal diameter. To study this, a T-helper-cell clone, D10.G4.1 was employed. This cell clone proliferates in the presence of Iak (Class II glycoprotein, MAC product) bearing M luminal diameter and specific antigen (conalbumin A) thus directly reflecting the AP capability of the M luminal diameter. Peritoneal M luminal diameter were harvested from B10.BR mice (H2k) and their AP was tested in vitro by incubating varying numbers of M luminal diameter with 2 X 10(4) D10.G4.1 cells/well and conalbumin (400 micrograms/ml) in the presence and absence of different concentrations of PGE2 or TXB2. Cultures were incubated for 72 hr, pulsed with [3H]-thymidine, and harvested. At concentrations of 10, 30, and 100 nM of PGE2, D10.G4.1 proliferations were 38, 35, and 20% of control, respectively (P less than 0.05 compared to control). TXB2 added at the above-mentioned concentrations did not suppress the proliferative response of D10. Thus, PGE2 but not TXB2 has a potent immunosuppressive effect on AP of peritoneal M luminal diameter.(ABSTRACT TRUNCATED AT 250 WORDS)

Immune mechanisms in autoimmune ocular disease

Aberrant expression of Class II MHC antigens (Ia) by non-immune cells is considered to be an important mechanism in the pathogenesis of autoimmune disease processes including those affecting the eye. It is suggested that circulating autoreactive T-cells are directed to their target organ as a result of aberrant expression of Ia antigens by the vascular endothelium of that organ. This hypothesis was tested in this study using two different models of severe ocular inflammation, induced by either S-antigen or bovine serum albumin (BSA). The retinal vascular endothelium becomes Ia + in S-antigen induced inflammation but not in inflammation induced by BSA. The accumulation in the eye of a T-cell line, ThS, specific for an ocular antigen (S-antigen), was compared in the two types of ocular inflammation and compared to that of another T-cell line, ThP, specific for a non-ocular antigen (PPD). In S-antigen induced inflammation, there was much greater accumulation of ThS than ThP whereas in BSA induced inflammation, both T-cell lines accumulated to the same extent but more than in uninflamed eyes. These results suggest that when the retinal vascular endothelium expresses Ia antigens during an inflammatory process, autoreactive T-cells will be specifically retained in the eye as a result of this and perpetuate the autoimmune destructive process.

Release of soluble interleukin-2 receptors (Tac peptide) in vivo during human immune responses to tuberculin

Cutaneous levels of soluble interleukin-2 receptor (Tac peptide) have been measured in tuberculin responses in 13 human volunteers by assaying the fluid present in suction-induced blisters at various times after injection of standard purified protein derivative of tuberculin (PPD). Low levels of Tac peptide were found in blisters without prior injection of PPD and in PPD-negative individuals, and maximal levels of Tac peptide were correlated with increased induration at 48 hr (r = 0.69, P = 0.04) in PPD-positive subjects. This is the first report of measurement of Tac peptide in vivo in a defined immune response in man, and may offer a new approach to the study of human immune function in vivo.

Serological characterization of macrophage hybridomas: identification of an interferon-gamma-inducible surface marker

Macrophage hybridoma clones prepared by fusion of splenic adherent cells with P388D1 tumor cells have previously been shown to be heterogeneous with respect to function at the clonal level. In this study the macrophage clones were phenotypically characterized by indirect RIA using a battery of rat MAbs to murine myeloid and lymphoid cell surface markers. All macrophage clones expressed the common leukocyte antigen T200 and the Mac-1 alpha and beta chains. Markers which were differentially expressed among the clones included class II antigens and the antigens detected by MAbs MIV 55, MIV 38, and 14G8. The antigens detected by the latter three MAbs were referred to as MBR-1, -2 and -3, respectively. Functional heterogeneity did not correlate with phenotypic heterogeneity among the macrophage clones. Treatment of macrophage clones with IFN-gamma resulted in a significant increase in the expression of class II antigens and induced the expression of MBR antigens on some clones which were constitutively negative for these markers. The clonal distribution and induction patterns of class II antigen as compared to MBR antigen indicated that regulation of expression of these markers was independent. In addition, the clonal distribution and induction pattern of MBR antigens, along with competitive binding studies using radiolabeled MIV 38 and 14G8 MAbs, suggested that the three MBR antigens were similar or closely associated molecules.

Involvement of antigen and I-J determinants in the induction of effector T suppressor cells by immune B cells

Immune B cells induce effector T suppressor cells in vitro. The B cells act as antigen-presenting cells, and express both I-A and I-J determinants. Antigen and I-J determinants are required for the induction of suppressor T cells by immune B cells, but I-A determinants are not. These findings indicate that precursors of suppressor T cells appear to recognize antigen in the context of I-J determinants on the surface of immune B cells.

Responsiveness of T cells to mutant major histocompatibility complex class I antigen. I. Obligatory dependence of proliferative response on the presence of stimulator type accessory cells

Proliferative response of splenic T cells of C57BL/6 mice to mutant major histocompatibility complex (MHC) class I antigen (H-2Kbm1) was examined with regard to the role of accessory cells. T cell proliferation in mixed lymphocyte culture (MLC) was not induced when accessory cells were removed from stimulator spleen cells by passage through Sephadex G-10 or nylon-wool column. Anti-Iab antibodies did not inhibit the proliferative response to class I antigen, whereas the same antibodies completely blocked the response to class II antigen (Iabm12). Accessory cells may not be mere presenters of MHC class I antigen because stimulator cells fixed with 0.05% paraformaldehyde lost the stimulating function. The proliferative response was partially recovered by the addition of recombinant interleukin 1 (IL-1) and/or IL-2 to MLC devoid of stimulator type accessory cells. It is concluded that stimulatory type accessory cells were obligatorily involved in the T cell proliferation, and the production of IL-1 by accessory cells is thought to play a critical role in this process.

Biological effects of Pseudomonas aeruginosa exotoxin A: lymphoproliferation of T lymphocytes in athymic mice

Pseudomonas aeruginosa exotoxin A has been observed to exert modulatory effects on the immune response. The present study examines the ability of exotoxin A to induce proliferation of splenocytes from athymic nu/nu mice. We observed that exotoxin A induced the proliferation of athymic nude splenocytes which could be abrogated by heating the toxin at 70 degrees C or by preincubation of the toxin with rabbit anti-exotoxin A antiserum. Photoaffinity-labelled toxin significantly induced splenocyte proliferation although the relative activity was reduced. Maximum nude splenocyte proliferation was observed at a toxin dose of 100 ng. This same dose was shown previously for athymic splenocytes to induce an enhanced response to the thymus-dependent (TD) antigen, sheep red blood cells (SRBC). The increased [3H]-TdR uptake in athymic splenocytes stimulated by exotoxin A was initiated by 24 hours and continued to day 10. Nude splenocytes depleted of Ig+ and Ia+ cells were induced to proliferate by exotoxin A. Cyclosporin A addition abrogated the ability of exotoxin A to induce proliferation. These results suggest that Pseudomonas aeruginosa exotoxin A can stimulate the proliferation of splenic T lymphocytes in athymic nu/nu mice.

Cell-mediated immunity to chemically xenogenized tumors. II. Evidence for accessory function and self-antigen presentation by a highly immunogenic tumor variant

To determine whether antigen-presenting ability might be involved in the superior immunogenicity of chemically xenogenized tumors over that of parental cells, we tested a murine lymphoma line xenogenized by a triazene derivative for expression of Ia antigens, ability to present soluble antigen in vitro, and production of factor(s) active in a mouse thymocyte assay. Results showed that Ia antigens, absent on nonimmunogenic parental L5178Y cells, were expressed on a xenogenized, highly immunogenic tumor variant (clone D), as detected by immunofluorescence. While the ability of parental cells to stimulate lymphocyte proliferation in vitro was lost on removal of Ia+ cells from the responder population, considerable augmentation of reactivity was observed upon depletion of Ia+ cells from the population of splenocytes responding to the xenogenized cells. Under these conditions, stimulation was blocked by anti-Ia antibodies, or an anti-L3T4 reagent or antibodies to the novel antigenic determinants induced by xenogenization. In addition, no stimulating activity was observed following exposure of clone D cells to glutaraldehyde or lysosomotropic agents such as chloroquine and ammonia. When the ability of clone D cells to present ovalbumin in vitro was assayed, it was found that the xenogenized cells could present the soluble antigen to specifically primed lymphocytes. Moreover, clone D cells could substitute for splenic adherent cells in the proliferative reaction of splenocytes to concanavalin A. Finally, when the supernate from clone D-cell culture pulsed with phorbol myristic acetate was tested in a mouse thymocyte assay, considerable IL-1-like activity was disclosed.

Plasmodium berghei: lymphocyte and macrophage dynamics in the spleen of Balb/c mice in the course of infection and after rechallenge of cured mice

The purpose of this study was to determine a possible correlation between the cell populations of the immune system in the spleen, and the failure of normal Balb/c mice to overcome a Plasmodium berghei infection. After primary infection, all splenic white cell populations increased in number. However, the ratios between the different cell populations changed markedly. Macrophages, which comprise 5-10% of normal white spleen cells, rose to 70-80?% during the lethal infection. Most of the macrophages lacked surface Ia antigens. A rise in macrophage precursors in the spleen was also observed. The lymphocyte population was characterized by a preferential increase of T-suppressor-cytotoxic (Tsc) cells resulting in an inversion of the Tsc/Thelper ratio. During chloroquine treatment, administered in order to cure infected mice, all splenic populations remained expanded but their quantitative proportions returned to normal. Secondary infection of cured mice did no cause an additional increase in the number of splenic white cells, nor did it affect the ratios between the various populations. It appears that normal quantitative relations between spleen cell populations is a hallmark of the host's capability to overcome infection with P. berghei. The failure of the immune system, as seen during a lethal infection, may be due to the preferential increase in immature, functionally defective macrophages and possibly T-suppressor lymphocytes. Alternatively, the changes in macrophages and T lymphocytes described could be a result of rather than the cause of the high parasitemia observed during P. berghei infection.

Up- and down-regulation of human lymphokine (IL-2)-activated killer cell induction by monocytes, depending on their functional state

Studies were made to determine whether freshly isolated monocytes from healthy donors could influence the induction of lymphokine (IL-2)-activated killer (LAK) activity. Highly purified lymphocytes (greater than 99%) and monocytes (greater than 90%) were isolated by counter-flow centrifugal elutriation from peripheral blood. Lymphocytes incubated for 4 days with IL-2 showed significant LAK activity against natural killer (NK) cell-resistant target (Daudi) cells, whereas monocytes treated for 4 days with IL-2 and/or IFN-gamma were not cytotoxic. Under the experimental conditions used, addition of monocytes to the lymphocyte cultures resulted in significant augmentation of the LAK activity, depending on the density of monocytes added. In contrast, monocytes stimulated by lipopolysaccharide (LPS) markedly suppressed LAK activity induced by IL-2, depending on the dose of LPS added. Similar up- and down-regulations of LAK cell induction by monocytes were observed with 4 lines of human lung cancer cells as targets for LAK activity. Although supernatants from untreated monocytes did not increase LAK induction, supernatants from LPS-stimulated monocytes suppressed LAK induction. The regulatory role of monocytes could not be replaced by the addition of exogenous interleukin I (IL-I) or tumor necrosis factor (TNF). Prostaglandin E did not seem to play a regulatory role, since addition of indomethacin did not affect the regulation of LAK cell induction by monocytes. These results clearly indicate that human monocytes may cause up- or down-regulation of the expression of IL-2-induced LAK activity, depending on their functional state.

Bovine mononuclear phagocytic cells: identification by monoclonal antibodies and analysis of functional properties

Monoclonal antibodies (mAb) which react with bovine monocytes have been produced. These include three mAb (P8, IL-A22 and IL-A24) that recognize the majority of monocytes and granulocytes in peripheral blood; two of these mAb were also shown to react with 30-40% of cells in bone marrow, including both monocytic and granulocytic cells, and with variable percentages of tissue macrophages. Thus these mAb can act as markers for myeloid cells in haemopoietic tissues and for monocytes in cell populations devoid of granulocytes. A further two mAb (IL-A23 and IL-A25) recognize monocytes and/or macrophages. The reactivity of one of these mAb (IL-A25) appears to be mainly restricted to pulmonary macrophages. The other mAb reacts with a variable proportion of blood monocytes and generally with a higher percentage of tissue macrophages, suggesting that its expression may relate to activation or maturation of monocytes. In order to study the functional properties of peripheral blood monocytes, techniques were developed for obtaining populations of peripheral blood mononuclear cells (PBM) depleted of monocytes to less than 0.2% and monocyte populations of greater than 97% purity. Removal of monocytes from PBM abrogated the capacity of the cells to proliferate in response to Con A and PBS, although addition of 2-mercaptoethanol to the cultures restored proliferation. In both allogeneic and autologous mixed leukocyte cultures (MLC), monocytes were required in the stimulator cell populations for induction of the proliferative responses, and both responses could be elicited with purified monocytes. However, proliferation in the autologous MLC occurred only with responder cell populations that were depleted of monocytes. Moreover, it was shown that addition of more than 5% unirradiated monocytes to the autologous MLC suppressed proliferation. These findings indicate that monocytes play an important role in the induction and regulation of cellular immune responses in cattle. Two of the mAb that react with monocytes and granulocytes were tested for their capacity to inhibit proliferative responses of PBM to mitogens, alloantigens or the soluble antigen, KLH.(ABSTRACT TRUNCATED AT 400 WORDS)

Removal of endotoxin from culture media by a polymyxin B sepharose column. The activity of contaminating endotoxin in culture media measured by the interleukin 1 inducing effect on human monocyte cultures and by the Limulus test

The in vitro study of monocytes (Mo) poses several problems. Minor contamination with endotoxin (ET) of media and utensils as well as adherence to glass or plastic surfaces may activate the cells and cause pronounced production of monokines. Many commercially liquid culture media were found to contain ET in concentrations above 25 X 10(-12) g/ml. A simple system for the removal of ET from media and solutions was established by use of a commercially available Polymyxin B Sepharose gel. To measure the lipopolysaccharide (LPS) binding capacity of the gel, known concentrations of LPS were added to culture media, which were passed through a column consisting of the Polymyxin B Sepharose gel. The content of ET and added LPS in media was measured by the Limulus amoebocyte lysate (LAL) test before and after passage of the column. The LPS-binding capacity of the gel was approximately 2.4 X 10(-6) g/10 ml. The biological activity of contaminating ET and added LPS in media, before and after passage of the column, was also characterized by the capacity of the media to induce interleukin 1 (IL-1) secretion in human Mo cultures. The content of IL-1 in Mo culture supernatants was determined by the mouse thymocyte costimulatory (LAF) assay. By comparison of the activity of ET in these different biological systems, it was demonstrated that 15-20 X 10(-12) g/ml of ET stimulate human Mo cultures to IL-1 secretion.

Heavy-metal mitogenesis: Zn++ and Hg++ induce cellular cytotoxicity and interferon production in murine T lymphocytes

Splenic and lymph node lymphocytes from Balb/c mice were activated in vitro by the heavy-metal cations, Zn++ and Hg++, as noted by the several-fold increases in 3H-thymidine incorporation at 144 h of culture. Optimal mitogenic concentrations of Zn++ and Hg++ were 200 microM and 10 microM, respectively. Data from experiments using T or B splenic lymphocytes enriched by cell passage over nylon wool columns, through use of athymic Nu/Nu mouse spleen cells, or by cell lysis with monoclonal anti-Thy-1 and antibody plus complement, indicated than Zn++ and Hg++ are mitogens for T cells. Removal of macrophages from spleen cells by treatment with carbonyl iron, followed by cell passage through nylon wool, eliminated the lymphocyte responses to Zn++ and to Hg++. Moreover, addition of macrophage-depleted lymphocytes to monolayers of resident peritoneal macrophages restored the lymphocyte responses to these mitogens. Both Zn++ and Hg++ activated splenic lymphocytes to display lectin-dependent cytotoxicity and to produce acid-labile interferon.

A functional and biochemical analysis of bovine class II MHC antigens using monoclonal antibodies

Monoclonal antibodies (MAbs) reacting with bovine (2) ovine (3), murine (1) or human (1) Class II MHC antigens were examined for reactivity with bovine peripheral blood leucocytes (PBL) and lymph node cells (LNC) by immunofluorescence, immunoprecipitation and the capacity to inhibit mixed lymphocyte responses (MLR), lectin- and antigen-induced blastogenesis. The 6 MAbs identified comparable percentages of Class II positive lymphocytes in PBL (40.8 to 54.2%) and LNC (6 to 11.5%) regardless of BoLA-A phenotype. Immunohistological staining of Class II MAb was localized principally to the lymphoid follicles in lymph nodes and to isolated epithelial reticular cells in the thymus. The anti-Class II MAb immunoprecipitated alpha- and beta- chains of 26-29K and 32-34K, respectively. These MAb inhibited proliferative responses in the MLR by between 25 and 74%, and diminished blastogenesis induced by specific antigens (purified protein derivative + PPD and ovalbumin) and B-lymphocyte mitogens (PPD, lipopolysaccharide and dextran sulphate) by between 45 and 75%, regardless of BoLA-A phenotype. In contrast, proliferation in response to concanavalin A and phytohaemagglutinin were unaffected by the anti- Class II MAb. Similarly these MAb did not affect lysis by cytotoxic T-lymphocytes, the activity of which was depressed by anti-Class I MAbs and monospecific alloantisera.