C-reactive protein levels in the differential diagnosis of brain abscesses

C-reactive protein (CRP) is a protein found in plasma at elevated concentrations during acute or chronic infections. As an aid in the differential diagnosis between brain tumor and abscess, the CRP levels were measured in 20 patients with intracranial mass lesions and the appearance of ring-like contrast enhancement on computerized tomography (CT) scans. In nine of these patients, the final diagnosis was abscess, based on either biopsy of the mass (eight patients) or the clinical course (one patient). In seven of the nine patients, there was a significant increase in CRP levels in two consecutive measurements. In particular, patients with cerebritis who were examined early in the course of the disease and who showed nonspecific CT scans exhibited extremely high levels of CRP. Two patients had no measurable CRP activity although they both had brain abscesses. In 12 patients harboring either gliomas or metastatic intracerebral tumors, CRP levels were significantly lower than those found in patients with brain abscesses but were nevertheless higher compared to those of a group of patients with benign tumors. It is concluded, therefore, that the measurement of CRP can have some value in the differential diagnosis between brain abscess and brain tumor. The measurement technique is inexpensive and is available in the clinical laboratories of most hospitals with a neurosurgical department.

Characterization of Chlamydia trachomatis serotypes by human T-lymphocyte clones

T cells primed to Chlamydia trachomatis serotypes A, F, and K were cloned by limiting dilution. All T-lymphocyte clones obtained reacted only with C. trachomatis antigens. The proliferative capacity of 89 clones was studied with autologous non-T cells as antigen-presenting cells and the chlamydia serotypes A, B, D, F, K, and LGV-2 as antigens. Most of the clones reacted to several of the chlamydia strains, indicating common antigenic determinants. Other T-cell clones reacted with only a few serotypes. On the basis of the proliferation of the T-cell clones to the chlamydia strains and to interleukin-2, different reactivity patterns were obtained, which possibly can be used to differentiate among the chlamydia strains.

The effect of short-term corticosteroid incubation on the alloactivating and antigen-presenting capacity of human epidermal Langerhans cells

The effects of short-term incubation with hydrocortisone and methylprednisolone on the alloactivating capacity and the ability of human epidermal Langerhans cells and peripheral blood monocytes to induce antigen (PPD)-specific T-lymphocyte responses were investigated. The Langerhans cells and the monocytes were treated with different concentrations of the steroids before being added to allogeneic T lymphocytes, and before, after or simultaneously with, pulsing with PPD. Neither steroid inhibited the alloactivating capacity of the Langerhans cells, but a dose-dependent reduction of the stimulatory capacity of antigen-pulsed Langerhans cells and monocytes was obtained with methylprednisolone. Hydrocortisone had inhibitory effects only at high concentration. The inhibition appeared to be due to suppression of the presentation of PPD in immunogeneic form to sensitized T cells.

Lack of cell-mediated cytotoxicity towards Chlamydia trachomatis infected target cells in humans

Induction of cell-mediated cytotoxicity towards Chlamydia trachomatis infected target cells was studied in humans. PHA-derived lymphoblasts, infected with inactivated or virulent LGV-2 chlamydial particles, were used as target cells. Chlamydial primed T cell blasts or specific, cloned T cells were used as effector cells. A highly sensitive 18 hours lytic assay employing 111In-labelled target cells was used. Specific cytotoxicity towards C. trachomatis infected target cells in humans could not be detected. This was the case regardless of the origin of the effector cells or the various protocols tested. However, this assay was capable of yielding significant positive results with effector cells primed to alloantigens. We conclude that cell-mediated cytotoxicity towards bacterial infected target cells probably does not play a major role.

Inhibition of the antigen activated T cell response by methylprednisolone is caused by inhibition of interleukin-2 (IL-2) production

A mechanism by which the steroid methylprednisolone inhibits the T cell proliferation normally seen in antigen driven cultures was investigated. At methylprednisolone concentrations less than 10 micrograms ml-1 inhibition of cellular proliferation was almost exclusively via the inhibition of the production of interleukin-2 by activated T cells. The steroid seemed to inhibit IL-2 production directly and not via reduced sensitivity to interleukin-1 by IL-2 producer T cells, or reduced IL-1 production by the antigen presenting monocytes. At methylprednisolone concentrations of greater than 10 micrograms ml-1 direct inhibition of the T cell receptor to antigen complexes presented by cooperating monocytes seemed the most likely explanation. T cells in the presence of antigen and monocytes and MP concentrations of greater than 10 micrograms ml-1 did not produce IL-2 and were incapable of expressing IL-2 receptors. The inhibiting effects of methylprednisolone therefore are via several mechanisms depending on the concentration of the steroid employed.

Endothelial growth factor production in cultures of human glioma cells

Human glioma cells derived from biopsied material were grown in tissue culture for periods of up to 2 weeks. Supernatants from these cultures were harvested at various intervals and their ability to enhance proliferation of cultured umbilical vein human endothelial cells was assessed. All of the supernatants tested contained some degree of endothelial cell mitogenic factor activity. The activity in the supernatants reached a maximum from cultures which were 4-8 days old and gradually decreased thereafter. Supernatants from the fibroblast monolayer were not significantly stimulatory for this endothelial cell model. On the other hand, supernatants from the glioma cultures did not increase the growth of human skin fibroblast or peripheral blood lymphocytes in culture. Extracts from bovine cartilage inhibited the mitogenic activity of the supernatants from glioma cultures.

HLA-DR3- and HLA-DR7-restricted T-cell hyporesponsiveness to gluten antigen: a clue to the aetiology of coeliac disease?

Coeliac disease (CD) is strongly associated with the human class-II HLA determinants HLA-DR3 and -DR7. We investigated the relative frequency of gluten-reactive T cells from DR3- or DR7-positive. CD patients and healthy controls who were heterozygous at the DR locus. We found a consistently and significantly lower frequency of gluten-reactive T cells when the antigen was presented by monocytes in conjunction with DR3 or DR7 than in conjunction with the other DR determinant of the T-cell donor. In contrast, the frequency of reactive T cells in these donors to other antigens was not reduced in conjunction with DR3 or DR7. These results indicate a specific immunoregulatory function associated with class-II HLA molecules. The reduced frequency of gluten-reactive T cells in association with HLA-DR3 or -DR7 may be directly involved in the development of CD.

Cell mediated lympholysis; a modified technique using 111indium-oxine-labelled targets

The isotope 51Cr generally used in the cell mediated lympholysis (CML) assay suffers from the disadvantage of low specific activity, poor incorporation and high spontaneous release, limiting the CML assay to 4-6 h. We have labelled PHA derived human lymphoblasts with the isotope 111indium (using 111indium-oxine) and evaluated these cells as targets in CML. The level of 111In-oxine incorporation decreased rapidly in the presence of serum; in the absence of serum approximately 85% of the available isotope in the supernatant was incorporated into the blasts. Under the labelling conditions used, spontaneous release was 1.6-2%/h on average allowing an effector phase of 18 h. About 5-8% of the released isotope was reutilized by the effector cells during an 18 h incubation period. Extending the CML assay from 6 to 18 h greatly increased the cytotoxicity. At an effector to target ratio of 25:1, the average per cent specific release increased from 15 to 50%. The use of 111In-oxine labelled targets in the CML therefore increases the sensitivity of the test and allows fewer effector and target cells to be used as compared with 51Cr techniques.

Cell-mediated cytotoxicity toward the donor in patients with well-functioning kidney grafts. Possible mechanism of specifically reduced cytotoxic response

Patients with well-functioning kidney allografts from one-HLA-haplotype--mismatched related donors have strongly reduced donor-specific cell-mediated cytotoxicity 2-10 years after having received their grafts. This could also be demonstrated in secondary in vitro cell-mediated lympholysis (CML). Even though secondary donor-specific CML did not exceed 10% at an effector-to-target cell ratio of 50:1, specific lysis of donor target cells increased significantly with increasing effector cell concentrations. The weak cytotoxicity toward the donor could be enhanced neither through pool-cell stimulation nor by adding exogenous Interleukin 2 (IL-2) during the induction phase. Furthermore, growth factors were produced in the cultures during the induction of cytotoxic cells in concentrations comparable to those of the sibling control. Thus no evidence could be obtained that lack of IL-2 was causing the decreased cytotoxicity in these patients. Our studies indicate that in vivo depletion of cytotoxic cells with high lytic efficiency is probably the reason for the strongly reduced donor-specific cytotoxicity.

Donor-specific decreased cell-mediated cytotoxicity in recipients of well functioning, one HLA haplotype-mismatched kidney allografts

Patients with well functioning kidney grafts from one HLA haplotype-mismatched related donors were studied 2 to 10 years after transplantation. No direct cell-mediated lympholysis (CML) toward donor cells was found. After in vitro sensitization in mixed lymphocyte culture, the recipient effector cells were not able to significantly kill donor target cells at an effector to target cell ratio of 50:1, while the HLA-A,B,D/DR-identical sibling of the recipient could generate strong cytotoxicity toward the donor at similar effector to target cell ratios. Nevertheless, the patient developed strong cytotoxicity toward third-party targets. Our findings indicate in vivo depletion of cytotoxic cells with specificity for donor antigens. No correlation between the mixed lymphocyte culture (MLC) response and the ability to generate cytotoxic cells could be found in recipient-donor combinations. In looking for in vivo generated suppressor cells toward the donor, a moderate suppression was found in three of six patients studied.

HLA-D restriction of antigen-specific proliferative T cell responses. Inhibitory activity of antisera against HLA determinants or stimulatory antigen

The specificity of the inhibitory activity of anti HLA-DR antisera on the proliferative response of human T cells to soluble antigens has been recently challenged. Furthermore, there are conflicting reports about the effect of antisera to the stimulatory antigen. Therefore, we investigated the inhibitory activity of different antisera on the proliferative response of T lymphocytes from sensitized donors to the antigens HSV and PPD. Alloantisera to DR specificities shared between antigen presenting cells (APC) and T cells displayed a strong inhibitory activity: alloantisera to HLA-DR specificities expressed only by APC or the T cell donor displayed lower or no inhibitory activity. Monoclonal antibodies to monomorphic determinants of HLA-DR molecules were inhibitory, but only when used at a high concentration. Antisera to HLA-ABC molecules and to HSV displayed little if any inhibition. These findings provide further evidence that the HLA-DR molecules as such in the APC membrane, which were also present during initial sensitization, are restriction elements for T cells.

Effect of methylprednisolone on human lymphocytes primed to alloantigens

Human lymphocytes were primed in mixed lymphocyte cultures (MLC) in the presence of the corticosteroid methylprednisolone (MP). The generation of proliferative-, cytotoxic- and suppressor cells after specific restimulation of the cultures was studied. Low doses of MP strongly inhibited the generation of secondary proliferative and cytotoxic cells. MP did not render these cells permanently unresponsive, as lymphocytes primed in the presence of MP as were still able to respond to the original stimulators in a primary fashion. In contrast, doses of MP as high as 10 micrograms/ml which are well above clinical levels, had no inhibitory effect on the induction of suppressor cells in these cultures. Our results indicate therefore, that steroids may prevent priming of specific cytotoxic and proliferative T cells, without inhibiting the induction of suppressor lymphocytes in secondary allogeneic cultures.

Histocompatibility antigens on astrocytoma cells

Biopsies tumour cells from astrocytoma-bearing patients were grown in primary culture for 3-5 days. Both low and high grade tumours were represented in the study. The cultured cells could be shown to express the HLA-A and -B antigens using a multispecific allo-antiserum and a rabbit anti-beta-2 microglobulin antibody. The tumour cells were negative for the HLA-DR determinants when tested with either rabbit anti-Ia-like antisera or specific anti-HLA-DR allo-antisera. They also failed to stimulate allogeneic lymphocytes in primary mixed lymphocyte-tumour cell cultures but stimulated lymphocytes primed to tumour cells in vitro. The tumour cells were also capable of stimulating autologous lymphocytes from the tumour-bearing patient in most of the combinations tested.

HLA antigens on glioma cells from short term cultures

Biopsied tumor cells from astrocytoma-bearing patients were grown in primary culture for 3-5 days. Both low and high grade tumors were represented in the study. The cultured cells could be shown to express the HLA-A and -B antigens using a multispecific allo-antiserum and a rabbit anti-beta-2 microglobulin antibody. The tumor cells were negative for the HLA-DR determinants when tested with either a rabbit anti-Ia-like antisera or specific anti-HLA-DR allo-antisera. They also failed to stimulate allogeneic lymphocytes in primary mixed lymphocyte-tumor cell cultures but moderately stimulated autologous lymphocytes from the tumor-bearing patient in most of the combinations tested.

Antigen-presenting properties of human vascular endothelial cells: inhibition by anti-HLA-DR antisera

Human vascular endothelial cells (EC) separated from the umbilical vein are capable of presenting antigen to in-vivo-sensitized T cells, leading to an immunoproliferative response to various antigens in vitro. Optimal T-cell response was only observed when the EC donor shared both HLA-D/DR determinants with the T-cell donor. The T-cell response normally observed when using antigen-pulsed EC was significantly and specifically inhibited by xeno- and allo-antisera reacting with the HLA-DR molecules. Moreover, antibodies reacting with the native antigen determinats (rubella virus) also appeared capable of inhibiting the response elicited by primed T cells to antigen-pulsed EC.

Vascular and renal distribution of HLA--DR-like antigens

Tissue sections of ethanol-fixed, paraffin-embedded specimens from human kidney, placenta and umbilical cord were studied by indirect immunofluorescence with a rabbit antiserum to HLA--DR antigens from B lymphocytes. Capillary walls in the kidney showed specific staining both in glomeruli and around tubuli. Conversely, HLA--DR-like antigens were not detected in the walls of larger vessels, in tubular cells, or in the epithelium of Bowman's capsule. HLA-DR-like antigens of kidney elements thus seemed to be restricted to capillary endothelial cells. In specimens from umbilical cord and placenta, HLA--DR-like antigens were not detected in the walls of capillaries or larger vessels. Isolated endothelial cells from the umbilical vein were likewise negative.

Presentation of viral antigens by human vascular endothelial cells in vitro

Endothelial cells (EC) separated from the umbilical vein were shown to be free of contaminating monocytes. EC could replace peripheral blood-derived macrophages as antigen-presenting cells for in vivo sensitized T cells towards a variety of viral antigens. The T-cell--CE-antigen response was also specificity inhibited by anti-HLA-DR antisera. T cells primed by antigen together with autologous macrophages could be restimulated by antigen pulsed HLA-D/DR identical EC in an antigen specific secondary response, indicating a similar mechanism for antigen presentation by EC or macrophages.