Ia-bearing T lymphocytes in man. Their identification and role in the generation of allogeneic helper activity

CD8 T cell memory recall is enhanced by novel direct interactions with CD4 T cells enabled by MHC class II transferred from APCs

Protection against many intracellular pathogens is provided by CD8 T cells, which are thought to need CD4 T cell help to develop into effective memory CD8 T cells. Because murine CD8 T cells do not transcribe MHC class II (MHC-II) genes, several models have proposed antigen presenting cells (APCs) as intermediaries required for CD4 T cells to deliver their help to CD8 T cells. Here, we demonstrate the presence of MHC-II molecules on activated murine CD8 T cells in vitro as well as in vivo. These MHC-II molecules are acquired via trogocytosis by CD8 T cells from their activating APCs, particularly CD11c positive dendritic cells (DCs). Transferred MHC-II molecules on activated murine CD8 T cells were functionally competent in stimulating specific indicator CD4 T cells. CD8 T cells that were “helped” in vitro and subsequently allowed to rest in vivo showed enhanced recall responses upon challenge compared to “helpless” CD8 T cells; in contrast, no differences were seen upon immediate challenge. These data indicate that direct CD8∶CD4 T cell interactions may significantly contribute to help for CD8 T cells. Furthermore, this mechanism may enable CD8 T cells to communicate with different subsets of interacting CD4 T cells that could modulate immune responses.

Immunisation with an allogeneic peptide promotes the induction of antigen-specific MHC II(pos) CD4+ rat T cells demonstrating immunostimulatory properties

BACKGROUND

The phenomenon of T cell stimulation by MHC class II expressing (MHC II(pos)) CD4+ T cells has been intensively investigated for T cell clones but, so far, not for native T cells. The extensive use of T cell clones may explain the inconsistent outcomes of T cell-mediated antigen-presentation. Therefore, we used freshly isolated primed rat CD4+ T cells induced by immunisation with an allogeneic peptide P1, which is involved in allograft rejection.

METHODS

MHC II(pos) and MHC II(neg) CD4+ T cells were isolated from popliteal lymph nodes of P1-immunised Lewis rats and were purified by combining depletion and positive selection steps. Purified MHC II(pos) CD4+ T cells and MHC II(neg) CD4+ T cells (10⁵ cells per well each) were autostimulated or restimulated with P1-loaded (33 μg/ml peptide P1) and subsequently irradiated (with 20 Gy) autologous DC.

RESULTS

Seven days after immunisation, a small population of MHC II(pos) CD4+ T cells was detectable (approximately 8.0% of total lymph node cells), as well as a large population of MHC II(neg) CD4+ T cells (up to 45%). Antigen-specific proliferation was observed for both T cell populations but only P1-loaded MHC II(pos) CD4+ T cells presented antigen presenting cell (APC) function for P1-primed T cells. Their inability to activate unprimed T cells may be due to impaired surface expression of costimulatory molecules (CD80 and CD86).

CONCLUSION

Immunisation with the allogeneic peptide antigen P1 induced antigen-specific MHC II(pos) CD4+ rat T cells demonstrating perfect APC function for primed T cells in vitro.

Antigen-independent acquisition of MHC class II molecules by human T lymphocytes

We report here that human T lymphocytes have the capacity of acquiring large amounts of MHC class II molecules from various types of antigen-presenting cells (APC) in an antigen-independent manner. The transfer of MHC class II molecules from APC to T cell required direct cell-to-cell contact and appeared to involve the interaction of numerous adhesion molecules between these cells. Depletion of cholesterol from the plasma membrane reduced the amount of MHC class II transferred onto the T cells. Most significantly, the newly acquired MHC class II molecules were capable of efficiently presenting antigen to T helper cells. These results suggest that T cells are able to interact with other T cells to regulate immune responses by presenting MHC peptide complexes that have been snatched away from nearby APC.

Activated peripheral blood mononuclear cells detected in lupus patients using cDNA coding for proliferating cell nuclear antigen

Abstract The expression of proliferating cell nuclear antigen (PCNA) mRNA in peripheral blood mononuclear cells (PBMCs) from patients with systemic lupus erythematosus (SLE) was measured by dot blot hybridization using a PCNA cDNA, and correlated with the percentage of PCNA-positive cells detected immunohistochemically using a monoclonal anti-PCNA antibody. PCNA-positive PBMCs were detected in 72.2% of SLE patients (n = 36), which is significantly more than among healthy controls. In addition, among those in whom PCNA expression was detected, the percentage of PBMCs expressing PCNA was significantly higher in SLE patients (mean 2.5% vs. 0.15%). The level of PCNA mRNA was increased in PBMCs from 83.3% of SLE patients, and was significantly correlated with the percentage of PCNA-positive cells (r = 0.54, P < 0.01) and with the disease activity score (r = 0.56, P < 0.01). A longitudinal study of two SLE patients confirmed that PCNA mRNA expression and the percentages of PCNA-positive cells varied in parallel with disease activity. Thus, an analysis of activated PBMCs from SLE patients using PCNA cDNA may be a useful method by which to estimate SLE disease activity.

Expression of CD80 and CD86 on peripheral blood T lymphocytes in patients with systemic lupus erythematosus

CD80 and CD86 were detected in high amounts on circulating T cells in the peripheral blood of some patients with systemic lupus erythematosus (SLE), using flow cytometry and monoclonal antibodies. Patients with other connective tissue diseases did not have a high percentage of T cells expressing CD80 or CD86 in their peripheral blood. CD80 was expressed mainly on CD4 T cells, whereas CD86 was expressed on CD8 T cells, and these two populations were associated with particular clinical features. These two molecules were expressed on different T-cell populations and might have different roles in the generation and regulation of immune responses. Since high expression of CD86 on T cells was detected much earlier than the appearance of clinical features and a high titer of anti-DNA antibody, it may be a useful parameter for predicting the flare of SLE.

Biological implications of HLA-DR expression in tumours

HLA-DR antigens show restricted tissue distribution in comparison with the more extensive expression of HLA class I molecules. This constitutive expression is genetically controlled by well-defined mechanisms. In addition, DR antigen expression can be induced by a variety of cytokines through different molecular genetic events that convert DR-negative epithelia into positive cells. In this review we analyse the two major pathological situations in which abnormal DR expression occurs: autoimmune diseases and tumour development. We hypothesize that conversion to DR-positivity may produce two opposite effects in both clinical situations: (1) a useful one in tumours associated with a good prognosis; and (2) a harmful one in autoimmune diseases with increased tissue damage.

Parkinson's disease and immunological abnormalities: increase of HLA-DR expression on monocytes in cerebrospinal fluid and of CD45RO+ T cells in peripheral blood

The etiology of Parkinson's disease is mainly unknown. Immune abnormalities have been described, but the cause of such abnormalities has not been resolved. We examined by two-colour flow cytometry HLA-DR antigen expression on monocytes from cerebrospinal fluid (CSF) and blood and, moreover, lymphocyte subpopulations (CD4+ CD45RO+, CD4+ CD45RA+, CD8+ CD11b+high) in peripheral blood from patients with Parkinson's disease compared with age-matched patients with other neurological diseases (OND) and tension headache. We found higher HLA-DR expression on CSF monocytes compared with blood monocytes. This difference was restricted to Parkinson's disease patients. T helper cell analysis revealed a decreased percentage of CD45RA+ "naive" and an increased percentage of CD45RO+ "memory" T cell subset from CD4+ T cells in peripheral blood of patients with Parkinson's disease compared with patients with tension headache. The proportions of CD8+ CD11b+high "suppressor" T cells remained unchanged, among the three patient groups compared. A selective loss of CD4+ CD45RA+ cells, previously observed in diseases like multiple sclerosis and Down's syndrome as compared with healthy controls suggests a common immunological abnormality in neurological disorders.

Preparation and characterization of a new monoclonal antibody CAF7 specific for a leukocyte activation antigen

A new murine hybridoma, CAF7, is raised using as an antigen the T-leukemic cell line CEM. It produces a monoclonal antibody (mAb) specific for an activation antigen on human lymphocytes. CAF7 stains monocytes, very weakly resting lymphocytes, and granulocytes, part of the thrombocytes, but not erythrocytes. After activation with phytohemagglutinin (PHA), CAF7 expression on peripheral lymphocytes rises as early as 5 hr post stimulation and 72-hr blasts express it at a considerable level. The cell lines Jurkat, CEM, MOLT4, Raji, Reh, K562, and MONOMAC6 are positive for CAF7. CAF7 immunoprecipitated an antigen, which when subjected to sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) under nonreducing conditions migrated as a single band with a molecular weight of 120-140 kD. Under reducing conditions, it appears as two bands at 90-100 and 40 kD. The pattern of expression and the biochemical characteristics of CAF7 do not match any of the clusters defined in the Leukocyte Typing Workshops, but do resemble that of a previously described antigen, 4F2.

Major histocompatibility antigen class II expressing resting porcine T lymphocytes are potent antigen-presenting cells in mixed leukocyte culture

The immune system of swine is unique in that the expression of CD4 and CD8 antigens defines four subpopulations of extrathymic resting T lymphocytes in blood as well as in lymphoid tissues. Recently, we documented an additional peculiarity of the porcine T lymphocyte population: a substantial proportion of resting T lymphocytes show constitutive surface expression of MHC II antigens (Saalmüller et al. 1991, Immunobiol. 183, 102). These cells belong predominantly either to the CD4-CD8+ or to the CD4+CD8+ T lymphocyte subpopulations. This report describes the antigen-presenting cell function of MHC II+ T lymphocytes in mixed leukocyte cultures. Experiments employing highly purified T lymphocytes as alloantigen-presenting stimulator cells resulted in a high proliferative and cytolytic alloantigen-specific T lymphocyte response. After separation of T lymphocyte stimulators into MHC II- and MHC II+ fractions, alloantigen-presenting cell function could be assigned to the MHC II+ T lymphocyte subset. Although the mechanisms involved in the response to alloantigen are not completely understood and may be different from conventional antigen presentation, this is the first report where naive resting MHC II+CD8+ T lymphocytes can be defined as antigen-presenting cells, presenting alloantigen to cells of their own lineage.

Podofilox-induced regression of Shope papillomas may be independent of host immunity

We tested the hypothesis that infiltrating leukocytes might contribute to papilloma destruction following podofilox treatment. New Zealand White (NZW) rabbits were inoculated with cottontail rabbit papillomavirus (CRPV) onto abraded areas of the dorsal skin. At 21 d after viral inoculation, 5.0% podofilox solution was applied to some papillomas, whereas others were used as controls. Three rabbits were sacrificed at each of three different periods after treatment initiation (1, 4, and 7 d). Four monoclonal antibodies (MoAbs), RG-16 (for B cells), L11/135 (specific for T cells), 2C4 (specific for class II antigen), and Ki67 (specific for proliferating cells), were used in an immunohistochemical study. All positive cells and total cells in the field were counted with an ocular grid. After 1 d of treatment, proliferation of papilloma cells was strongly suppressed in treated papillomas, but leukocytic infiltration was not altered. At 4 d and 7 d of treatment, there were substantial increases (about two to three times) in the numbers of B and T cells and class II-expressing leukocytes. The upper layers of the papillomas were highly necrotic and cell proliferation was absent in all layers. These data support the view that podofilox has a direct toxic effect on papilloma tissue. Leukocyte infiltration is not strongly associated with papilloma tissue and may not contribute to papilloma destruction.

Immunohistochemical detection of tissue-infiltrating lymphocytes in mild urothelial dysplasia

The presence and distribution of immunocompetent cells in normal and dysplastic urothelium of the bladder were investigated in 3 patients. Using an indirect immunoperoxidase staining procedure, monoclonal antibodies reacting with B (Leu12+) and T (Leu4+) cells, cells of the suppressor/cytotoxic (Leu2a+), helper/inducer (Leu3a+) and natural killer (Leu7+) phenotypes, monocyte-macrophages (LeuM3+), and cells expressing interleukin-2 receptor and HLA-DR antigen (HLA-DR+) were tested in all specimens. The results confirmed the presence of a well ordered and compartmentalised distribution of immunocompetent cells in the normal mucosa far from dysplasia. There was an increased number of lymphocytes in the hyperplastic/dysplastic urothelium with associated Von Brunn's nests. Leu2a+ cells, HLA-DR expressing cells and monocyte-macrophages were present inside the epithelium, particularly within dysplasia and von Brunn's nests, but the Leu3a+/Leu2a+ ratio was not inverted (0.48 + 0.1 to 0.74 + 0.2). These findings reveal that in mild urothelial dysplasia with von Brunn's nests there is a spatial modification of the immunological barrier associated with the mucosa.

Analysis of peripheral blood lymphocyte cell surface density of functional and activation associated markers in young and old hemodialysis patients

Aging has been associated with specific shifts in various peripheral blood immune competent cell subsets. As part of pre-transplant immune profile evaluation possible parallel age-related changes in mean T-cell surface density of several cluster differentiation and activation linked antigens were into 2 groups: group 1-114 patients 40 years old or younger and group 2-36 patients 55 years old or older. Peripheral blood CD3+, DR+, CD3+DR+, CD4+, CD4+DR+, CD8+, CD8+DR+, CD56+, CD8+CD56+, CD3+IL-2-R+ and CD3+TR+ (interleukin-2 and transferrin receptors bearing CD3+ cells respectively), all mononuclear cells expressing IL-2-R and TR, and CD4+CD45+ cell subsets were analyzed and enumerated by 2-color flow cytometry. Subset relative levels as well as absolute counts were recorded. Cell surface density computation was performed using a computerized mathematical model based on fluorescence intensity vector analysis and cell size score determination based on light scatter pattern from raw data obtained by flow cytometry studies. Younger age was significantly associated with higher absolute cell count of CD3+ (p < 0.001), DR+ (p < 0.05), CD4+ (p < 0.01), CD8+ (p < 0.005), CD3+IL-2-R+ (p < 0.05), CD3+TR+ (p < 0.03) and IL-2-R+ (p < 0.05). Older patients had a slightly higher mean absolute count of CD4+CD45+ subset (p not significant) and significantly higher mean count for CD8+CD56+ cell subset (p < 0.001). When cell subset levels were compared between the 2 groups as the relative fraction of cells expressing a given marker out of all mononuclear cells gated out by flow cytometry, younger age was significantly associated with higher levels of CD3+ (p < 0.005), CD8+ (p < 0.001), CD4+DR+ (p < 0.004), CD3-TR+ (p < 0.05) and CD8+IL-2-R+ (p < 0.05). In contrast, slightly higher subset levels of CD56+ (p not significant), and significantly elevated levels of CD8+CD56+ (p < 0.0019) and CD4+CD45+ (p < 0.004) were observed in the older patients. Cell surface density analysis showed that younger patients had higher mean density per cell of CD3 (p < 0.05), CD8 (p < 0.001), IL-2-R on CD3+ cells (p < 0.05) and TR on CD3+ cells (p < 0.05). Mean cell surface density of CD56 on all CD56+ cells as well as on CD8+ cells was higher in older individuals (p < 0.001 and p < 0.003, respectively).(ABSTRACT TRUNCATED AT 400 WORDS)

Donor CD8 cells prevent allogeneic marrow graft rejection in mice: potential implications for marrow transplantation in humans

Numerous experimental models have demonstrated that graft-vs.-host disease (GVHD) does not occur in irradiation chimeras when the graft does not contain mature, immunocompetent T lymphocytes, but clinical studies have shown that T cell depletion of donor marrow can be associated with a greatly increased risk of graft failure. We have developed a model where engraftment of (C57BL/6J x C3H/HeJ)F1 (B6C3) marrow in 800-cGy-irradiated (BALB/cJ x C57BL/6J)F1 (CB6) recipients depends on the presence of donor T cells in the graft. Recipients transplanted with 5.0 x 10(6) marrow cells depleted of T lymphocytes showed host lymphoid and myeloid reconstitution, whereas recipients transplanted with the same marrow plus 2.5 x 10(5) purified donor T cells showed donor reconstitution. Adding as few as 0.5 x 10(5) CD8-enriched donor T cells to marrow grafts containing 5.0 x 10(6) T cell-depleted donor cells was sufficient to enable donor reconstitution, while surviving recipients transplanted with the same marrow and 0.5-2.5 x 10(5) CD4-enriched donor cells showed only host reconstitution. To address the question of whether donor CD4 cells could facilitate engraftment under conditions where GVHD would not represent a limiting factor, engraftment of bm1 marrow was tested in major histocompatibility complex (MHC) class I-disparate B6.Ly5a recipients. Results indicated that the donor CD8-enriched population was at least fivefold more active than the CD4-enriched population for facilitating allogeneic marrow engraftment in this strain combination. Thus, the lymphokines and MHC class II-specific cytotoxic T cells generated by CD4 cells were relatively ineffective for enhancing engraftment, possibly reflecting the fact that the host T cells that contain effectors responsible for causing rejection do not express MHC class II antigens. The ability of donor CD8 cells to facilitate engraftment could reflect the activity of a cytokine uniquely elaborated after recognition of an MHC class I disparity. More likely, the graft-enhancing effect of donor CD8 cells may result from the generation of MHC class I-specific or class I-restricted cytotoxic T cells that recognize the host CD4 and CD8 cells responsible for causing rejection. The possibility remains that other mechanisms such as veto inactivation of host T cells by donor CD8 cells may also contribute to the graft-enhancing effect.

Human T cell autoimmunity against myelin basic protein: CD4+ cells recognizing epitopes of the T cell receptor beta chain from a myelin basic protein-specific T cell clone

We have investigated whether the normal immune system contains T cells that are able to recognize T cell receptor (TcR) determinants of autologous autoantigen-specific T cells. The T cell clone HW.BP3, specific for myelin basic protein (MBP) was isolated from a healthy donor. HW.BP3 is restricted by HLA-DR2a, and reacts to human MBP 139-153. The expressed alpha beta TcR genes of HW.BP3 were cloned and sequenced, and the sequences analyzed for potential T cell epitopes. Two synthetic peptides, one from the VDJ beta junctional (beta 1) and one from the V beta region (beta 2) of the TcR of HW.BP3, were used to select four TcR peptide-specific T cell lines from the donor of HW.BP3. All anti-TcR lines had the phenotype CD3+/CD4+/HLA-DR+/CD25+/CD45RO+, and recognized the antigen in the context of HLA-DR. Three anti-TcR lines, which had been selected for reactivity to peptide beta 1, recognized exclusively this peptide restricted by HLA-DR2b. One anti-TcR line, selected for peptide beta 2, responded to both peptides beta 1 and beta 2 when presented by autologous blood mononuclear cells, but not by HLA-DR2a- or HLA-DR2b-transfected L cells. All TcR peptide-specific T cell lines were efficiently cytotoxic. They specifically lysed autologous macrophages or HW.BP3 line cells in the presence of exogenous peptide antigen. In contrast, HW.BP3 did not present endogenous TcR peptides to the anti-TcR lines. The results demonstrate that the normal human immune system contains not only autoantigen-specific T cells, but also T cells that recognize antigenic determinants of autologous autoreactive TcR.

Activation of the HLA-DRA gene in primary human T lymphocytes: novel usage of TATA and the X and Y promoter elements

Human T lymphocytes express human leukocyte antigen (HLA)-DR-alpha (DRA) upon mitogenic or antigenic stimulation. DR+ T cells are also found in a number of inflammatory and autoimmune diseases and have a proposed role in these diseases. The molecular mechanism of DR regulation in untransformed blood T lymphocytes was studied here by transient transfection of DRA-chloramphenicol acetyltransferase reporter gene constructs. Several novel features of this regulation were observed. During the early stages of T-cell activation by mitogens or antigens, strong promoter induction was exhibited with the proximal 43 bp of the DRA promoter which contains a TATTA motif. Addition of upstream X and Y DNA elements augmented the response. This contrasts with data from transformed cell lines in which the proximal 43 bp produced no detectable promoter function, and the inclusion of X and Y elements is essential for basal level expression. Mutation of the TATTA motif or substitution with a functional but different TATA element produced errant initiation and greatly reduced gene expression. Interestingly, T lymphocytes from a normal donor were DR+ prior to in vitro stimulation, and again, strong promoter activity was observed with 43 bp of proximal sequence. Unexpectedly, the presence of the X and Y elements correlated with a suppression of class II promoter function and surface antigen expression. This study of nontransformed lymphocytes reveals several novel features of DRA gene regulation and underscores the value and necessity of such studies.

Activation of the HLA-DRA gene in primary human T lymphocytes: novel usage of TATA and the X and Y promoter elements

Human T lymphocytes express human leukocyte antigen (HLA)-DR-alpha (DRA) upon mitogenic or antigenic stimulation. DR+ T cells are also found in a number of inflammatory and autoimmune diseases and have a proposed role in these diseases. The molecular mechanism of DR regulation in untransformed blood T lymphocytes was studied here by transient transfection of DRA-chloramphenicol acetyltransferase reporter gene constructs. Several novel features of this regulation were observed. During the early stages of T-cell activation by mitogens or antigens, strong promoter induction was exhibited with the proximal 43 bp of the DRA promoter which contains a TATTA motif. Addition of upstream X and Y DNA elements augmented the response. This contrasts with data from transformed cell lines in which the proximal 43 bp produced no detectable promoter function, and the inclusion of X and Y elements is essential for basal level expression. Mutation of the TATTA motif or substitution with a functional but different TATA element produced errant initiation and greatly reduced gene expression. Interestingly, T lymphocytes from a normal donor were DR+ prior to in vitro stimulation, and again, strong promoter activity was observed with 43 bp of proximal sequence. Unexpectedly, the presence of the X and Y elements correlated with a suppression of class II promoter function and surface antigen expression. This study of nontransformed lymphocytes reveals several novel features of DRA gene regulation and underscores the value and necessity of such studies.

Peptide-induced proliferation and lymphokine production in human T cells in the absence of antigen-presenting cells: role of T-cell activation state and costimulatory signals

The role of T-lymphocytes as antigen-presenting cells (APCs) for other T cells was investigated. Activated rabies-virus-specific human T-cell clones were shown to present peptide to class II major histocompatibility complex (MHC)-restricted T cells of a different fine specificity, resulting in lymphokine production and cell proliferation. Furthermore, purified and activated antigen-specific T cells could produce lymphokines and proliferate as a result of the addition of antigenic peptide in the absence of APC. The functional response of T cells to peptide in the absence of APC was amplified by the addition of phorbol ester (PMA) and was inhibited with antibodies specific to class II MHC or to the CD2 molecule. Experiments performed in single-cell suspension cultures using semisolid medium prepared with 1% agar demonstrate that T-cell proliferative and lymphokine responses to peptide both in the presence and absence of APC require the interaction of T-cell antigen receptor (TCR) molecules with class II MHC-peptide complexes on different cell surfaces (cell-cell contact). On the other hand, peptide self-presentation, which occurs by the binding of TCR with class II MHC-peptide complexes on the same cell surface (at the single-cell level), resulted in T-cell activation (i.e., high expression of surface CD2, CD25, and HLA-DR molecules), without proliferation or lymphokine secretion, a pattern observed in the induction of T-cell anergy by antigen. The results are discussed in terms of the role of class II MHC molecules on activated T-lymphocytes, which enable these cells to function as "professional APC" in the development of T-cell regulatory networks.

Morphometric analysis and identification of infiltrating leucocytes in regressing and progressing Shope rabbit papillomas

Spontaneous regressions of papillomavirus lesions frequently occur in both human and animal infections. The mechanism by which this occurs is currently unknown. Mononuclear infiltrates are found in regressing human and rabbit papillomas. To assess the potential functional role of these infiltrates in regression, we have characterized and quantitated the cell types present in regressing rabbit lesions. Forty New Zealand white rabbits were inoculated with cottontail rabbit papillomavirus (CRPV) at 2 sites on the dorsal skin. All tumors on 6 rabbits markedly decreased in volume within 6 to 8 weeks of inoculation. Tumors on 4 of these 6 regressor rabbits were studied by immunohistochemistry. Regressor papillomas had conspicuous leucocytic infiltrates, most concentrated at the epithelial basement membrane, and often obliterating the basal cells of the germinal layer. Infiltrating leucocytes were also concentrated in the subjacent dermis immediately beneath the basement membrane. The infiltrates gradually lessened at increased depths in the dermis. In contrast, progressor papillomas contained fewer leucocytes, which were randomly distributed in the dermis. The phenotype of the infiltrating leucocytes was examined in 4 regressing and 12 progressing papillomas. In regressing papillomas, infiltrating leucocytes were predominantly T cells (68.0%), with relatively few B cells (7.4%). Progressing papilloma dermis contained fewer T cells and B cells than regressing papillomas. Most of the infiltrating T cells in regressing papillomas were labelled with a rabbit MHC-class-II-specific monoclonal antibody (MAb) (2C4), in contrast to only a small number in progressing papillomas. In addition to the leucocytic infiltrates, keratinocytes in regressing, but not in progressing, papillomas, frequently exhibited strong 2C4 staining. These results demonstrate that infiltration with T cells expressing rabbit class II is characteristic of regressing Shope papillomas and strengthens the assertion that cell-mediated immunity is the mechanism of Shope papilloma regression.

Expression of class I and II human leukocyte antigens by thyrocytes and lymphocytic infiltration on human thyroid tumors. An immunofluorescence study

Surgical thyroid sections from 30 papillary carcinomas (PC), six medullary carcinomas (MC), three anaplastic carcinomas (AC), two follicular carcinomas (FC), and 16 adenomas (AD) were examined with an indirect immunofluorescence technique employing different monoclonal antibodies to evaluate the expression of human leukocyte antigen (HLA)-A, B, C (Class I) and DR, DP, DQ (Class II) by thyrocytes, together with the phenotype and distribution of inflammatory cells. Ten PC and four FC were also investigated for the presence of intercellular adhesion molecule-1 (ICAM-1). In situ deposits of immunocomplexes and circulating thyroid autoantibodies were also evaluated. An increased expression of Class I antigens was found in all PC and FC, in 33% of MC and AC, and in 31% of AD. An anomalous expression of Class II antigens was observed in 70% of PC, in 50% of FC, in 33% of AC, in 19% of AD, and in none of the MC. Expression of DP or DQ was revealed only in a portion of the DR-positive glands. A reduction of microsomal autoantigen expression was found. No ICAM-1-positive thyrocytes were detected. A moderate T-lymphocytic infiltrate was noticed only in PC, where it was correlated with DR and DP and/or DQ coexpression. B-cells and natural killer cells were virtually absent. The authors speculate that the weak Class II antigens expression, together with the partial or complete loss in microsomal autoantigen and the absence of ICAM-1 by thyrocytes, may account for the limited engagement of immunocompetent cells observed in thyroid tumors.

Markers of T lymphocyte activation in HLA-B8, DR3 positive individuals

Many autoimmune diseases are associated in Caucasians with HLA-B8 and/or HLA-DR3 antigens. There is evidence that bearers of these antigens may display significant changes in immune parameters when compared to individuals not having these antigens. Recently, increased numbers of blood activated T lymphocytes have been reported in the majority of these diseases. The increase in activated blood T lymphocytes is paradoxically characterized by an in vitro impairment of T cell activation. Particularly, an inadequate production of interleukins has been observed. We have studied blood levels of activated T cells in HLA-typed, healthy subjects. The results show that the percentage of activated T cells, as recognized by monoclonal antibodies anti-CD25, anti-Ia and anti-MLR3, was more frequent in HLA-B8, DR3 positive individuals. On the other hand, in the 24 h, PHA stimulated cultures IL-2, IFN-gamma and the percentage of T cells CD25 positive were decreased. Thus, there was an apparent discrepancy between the increase of blood activated T cells and the in vitro impaired T cell activation. Since there is evidence that HLA-B8, DR3 positive subjects are genetically low responders, a possible reason for the discrepancy might be their relative inability to remove antigenic stimuli from the body. In this case, the increased number of activated blood T cells may reflect a cellular activation caused by persistent antigenic stimulation.

Phylogeny of immune recognition: antigen processing/presentation in channel catfish immune responses to hemocyanins

Studies were conducted to address the role(s) of antigen (Ag) processing/presentation in channel catfish immune responses. Vigorous and specific secondary in vitro proliferative and antibody (Ab) responses were obtained to keyhole limpet and Limulus polyphemus hemocyanins with peripheral blood leukocytes (PBL) from catfish previously primed in vivo with Ag. In addition, such antigen-specific in vitro proliferative and Ab responses were efficiently elicited by antigen-pulsed and subsequently paraformaldehyde-fixed autologous PBL used as putative antigen-presenting cells (APC) but not by APC fixed prior to Ag pulsing. Treatment of these putative APC with lysosomotropic agents, protease inhibitors, or the ionophore monensin prior to or during pulsing with Ag significantly inhibited both in vitro responses. Furthermore, the use of radiolabeled protein indicated that both untreated and inhibitor-treated PBL but not erythrocytes take up Ag; however, only untreated PBL were able to degrade Ag. Immune restriction was indicated by the use of allogeneic PBL as APC in that only strong MLRs were generated with no detectable antibodies produced in vitro. Finally, the employment of isolated leukocyte subpopulations demonstrated that both catfish B (sIg+) lymphocytes and monocytes were efficient Ag presentors.

Cytotoxic T cell recognition of an endogenous class I HLA peptide presented by a class II HLA molecule

Human leukocytes were stimulated in vitro with peptides corresponding in sequence to the highly variable helix of the alpha 1 domain of various HLA-B and -C molecules. A CD4+ CD8- cytotoxic T cell line, CTL-AV, that is specific for the HLA-B7 peptide presented by HLA-DR11.1 was obtained. The HLA-DR11.2 molecule, which only differs at three residues from HLA-DR11.1, did not present the HLA-B7 peptide to CTL-AV. Peptides from the alpha 1 domain helix of other HLA-A and HLA-B molecules, but not HLA-C molecules, competed with the HLA-B7 peptide for binding to HLA-DR11.1. A cell line (WT50) that coexpresses HLA-B7 and HLA-DR11.1 was killed by CTL-AV in the absence of any added HLA-B7 peptide. The processing and presentation of HLA-B7 in these cells appears to be through the endogenous, and not the exogenous, pathway of antigen presentation. Thus, Brefeldin A inhibits presentation and chloroquine does not. Furthermore, introduction of purified HLA-B7 molecules into HLA-DR11.1+, HLA-B7- cells by cytoplasmic loading via osmotic lysis of pinosomes, but not by simple incubation, rendered them susceptible to CTL-AV killing. These results provide an example of class II major histocompatibility complex (MHC) presentation of a constitutively synthesized self protein that uses the endogenous pathway of antigen presentation. They also emphasize the capacity for presentation of MHC peptides by MHC molecules.

Histocompatibility antigen expression in pulmonary carcinomas as indication of differentiation and of special subtypes

In 70 human carcinomas of the lung the expression of histocompatibility antigens (HLA) was investigated by using monoclonal antibodies in frozen sections. The immunmoreactive tumor volume was determined morphometrically. The tumor types showed a different pattern of HLA expressions. In squamous cell carcinomas (SQC) and small cell carcinomas (SCC) the HLA-A,B,C expression varied in a great range from 0% to 100% of positive tumor volume. For the most part, HLA-DR was not demonstrable. In adenocarcinomas (AC) and large cell carcinomas two different populations were observed. One showed a pattern of HLA expression as seen in SQC. Electron microscopically these AC (type 1) (AC/1) were characterized by intracytoplasmic mucin granules indicating a phenotypical relationship to goblet cells. The other--nearly 50% of adenocarcinomas and one third of large cell carcinomas--expressed both HLA antigens homogeneously in the total tumor volume. Electron microscopically the characteristics of type II pneumocytes and Clara cells were seen in tumor cells of these AC (type II) (AC/II), consisting in lamellar bodies and apically located electron-dense granules. In SQC and AC/I a significant correlation was found between grades of differentiation and mitotic activity on the one side, and expression of HLA-A,B,C on the otrher. The loss of HLA-A,B,C expression seemed to be an indication of a lower grade of differentiation; the smalles expression of HLA-A,B,C occurred in SCC.

Evolution of the MHC: antigenicity and unusual tissue distribution of Xenopus (frog) class II molecules

Antibodies that recognize Xenopus class II molecules have been developed. Mouse monoclonal antibodies were prepared by immunizing BALB/c mice with frog MHC antigens that had been partially purified with alloantisera, and by immunizing mouse spleen cells in vitro with activated Xenopus T lymphocytes. In addition, five mouse monoclonal antibodies specific for human class II antigens were found to cross-react with Xenopus class II antigens. A.TH mice, which do not express E class II molecules, always produce immunoprecipitating antibodies reactive with frog class II molecules after immunization with frog lymphocytes; other mouse strains rarely produce such antibodies. Two of the monoclonal antibodies raised against frog class II molecules recognize the denatured class II beta chain on Western blots, and the other three appear to recognize only the class II heterodimeric complex. The antibodies display differential reactivity with the allelic class II products of Xenopus. The monoclonal antibodies react with all adult lymphocytes in the spleen and peripheral blood, T cells and B cells having equivalent levels of class II antigens per cell. Class II molecules are "differentiation antigens" on adult thymocytes as the expression is greatest on the mature medullary population. The number of class II molecules/lymphocyte increases after culturing in medium containing fetal bovine serum. Sequential immunoprecipitation and isoelectric focusing experiments have shown that cell surface class II molecules immunoprecipitated with the monoclonal antibodies are the same as those immunoprecipitated with the cross-reactive antiserum specific for DR antigens which was previously used to identify frog class II molecules.

HLA-DP+ T cells and deficient interleukin-2 production in patients with systemic lupus erythematosus

In patients with systemic lupus erythematosus (SLE), frequency of the T cells positive for HLA-DP, one of the major histocompatibility complex (MHC) class II molecules, was markedly increased in peripheral blood lymphocytes (PBL), in association with an increase in the amount of specific cytoplasmic transcript of the HLA-DP gene segment. Cell cycle analysis showed that HLA-DP is an early activation marker of T cells and that the high ratios of HLA-DP+ T cells from SLE patients are associated with high frequency of T cells at early activation phases, mainly of G1A. Initial high ratios of HLA-DP+ T cells decreased to a great extent during 4 days of in vitro culture, in the absence of mitogens. This event was associated with decreases in the amount of HLA-DP transcript and the disappearance of activated T cells. Studies on the interleukin 2 (IL-2) production of T cells from patients with SLE demonstrated that while the PBL rich in HLA-DP+ T cells show a markedly low production of IL-2, preculture of these PBL restores the ability to produce IL-2. Thus, it appears that the T cells in patients with SLE are essentially intact with regard to the capacity to produce IL-2 and that T cell activation events continuously occurring in SLE patients are related to a deficiency in IL-2 production. The possible underlying mechanisms are discussed.

Selective expression of class II MHC isotypes by MLC-activated human T lymphocytes

Although activated human T cells express class II MHC molecules, the biologic significance of this event is not understood. Using two-color flow cytometry, we have analyzed the expression of HLA-DR, -DQ, and -DP isotypes by T cells following activation by allogeneic lymphoblastoid B-cell lines. Within the CD3+ population, transient expression was observed at 1 day following initiation of culture, which preceded a dramatic and sustained increase around 6-7 days. DR expression was always highest, followed by DP and DQ with DP expression usually somewhat higher than DQ. At day 8, three populations were observed consisting of DR+DP+DQ+ (60%), DR+DP+ (69%), and DR+ (75%) T cells. Interestingly, DQ+ or DP+ but DR- T cells were not observed. These patterns of class II isotype expression were similar in CD2+, CD4+, and CD8+ subgroups and suggest that class II molecules are selectively expressed on T cells and may play a role in the regulation of T-cell responses to alloantigens.

HLA-DP-positive T cells in patients with systemic lupus erythematosus

HLA-DP+ T cells in peripheral blood from 23 patients with systemic lupus erythematosus (SLE) were examined using two-colour flow cytometry analysis. A marked increase of HLA-DP+ T cells was observed in patients with SLE (20.5-98.7%; 59.8 +/- 20.8%) in comparison to normal subjects (1.3-20.6%; 11.1 +/- 7.2%), and the ratio of these cells greatly exceeded that of the HLA-DR+ T cells (6.5-49.1%; 21.5 +/- 12.7%). This high frequency of HLA-DP+ T cells in patients with active SLE decreased with prednisolone therapy. When the lymphocytes from normal subjects were stimulated with PHA in vitro, HLA-DP+ T cells increased from 1.8 to 59.2%. Therefore, it appears that the HLA-DP antigen expression on T cells is a practical marker for monitoring changes in the proportion of activated T cells in patients with SLE during the course of therapy.

Activated peripheral blood mononuclear cells detected by murine monoclonal antibodies to proliferating cell nuclear antigen in active lupus patients

Hybridoma producing monoclonal antibody to proliferating cell nuclear antigen (PCNA/cyclin) (TOB7, IgG1 kappa) was newly established. Using TOB7, PCNA was detected in the peripheral blood mononuclear cells (PBMC) in patients with systemic lupus erythematosus (SLE). Forty-four of 58 patients with SLE had PBMC expressing PCNA. The percentage of PCNA-positive PBMC in patients with SLE was 0-20% (mean: 2.63%) which was significantly higher (P less than 0.01) compared with normal controls (mean: 0.18%), patients with rheumatoid arthritis (mean: 0.83%), and patients with mixed connective tissue disease (mean: 0.38%). Patients with high numbers of PCNA positive PBMC tended to complicate pulmonary disorders (P less than 0.005), especially pulmonary fibrosis (P less than 0.005). In addition, the percentage of PCNA-positive cells in SLE patients correlated with the disease activity (r = 0.45, P less than 0.01). The lymphocyte subsets of PCNA-positive PBMC were examined, and most of those cells belonged to CD4- or CD8-positive T-cell populations in three lupus patients. Our findings indicate that PCNA-positive activated PBMC are present in SLE patients and the percentage of PCNA-positive PBMC may be used as an indicator of disease activity.

Contingent genetic regulatory events in T lymphocyte activation

Interaction of antigen in the proper histocompatibility context with the T lymphocyte antigen receptor leads to an orderly series of events resulting in morphologic change, proliferation, and the acquisition of immunologic function. In most T lymphocytes two signals are required to initiate this process, one supplied by the antigen receptor and the other by accessory cells or agents that activate protein kinase C. Recently, DNA sequences have been identified that act as response elements for one or the other of the two signals, but do not respond to both signals. The fact that these sequences lie within the control regions of the same genes suggests that signals originating from separate cell membrane receptors are integrated at the level of the responsive gene. The view is put forth that these signals initiate a contingent series of gene activations that bring about proliferation and impart immunologic function.

Interleukin-2 production and interleukin-2 receptor expression in children with newly diagnosed diabetes

In the present study, we investigated the interleukin-2 (IL-2) production and the proliferative responses by peripheral blood mononuclear cells (PBMNC) of 23 children suffering from insulin-dependent diabetes mellitus (IDDM). In addition, the presence of circulating activated T lymphocytes expressing the interleukin-2 receptor (IL-2 R) and HLA-DR antigens was evaluated. The patients were tested at hospital admittance, before starting insulin treatment. Decreased IL-2 production by phytohemagglutinin (PHA)-activated PBMNC of IDDM patients was observed when compared to normal donors. In contrast, the proliferative responses of PBMNC to PHA and Con A were in the normal range. The expression of IL-2 R on patient's lymphocytes was not different from that observed in normal donors, whereas the relative and absolute number of HLA-DR+ T cells was increased. These results confirm the presence in IDDM patients of an imbalanced cellular immune response and demonstrate that the IL-2 deficiency is already present at the diagnosis and is not correlated with insulin administration.

Analysis of host-virus interactions in AIDS with anti-gp120 T cell clones: effect of HIV sequence variation and a mechanism for CD4+ cell depletion

The primary human T cell response to HIV was analyzed by isolating from seronegative donors T cell clones specific for HIV gp120. T cell epitopes restricted by different MHC elements were identified within gp120, and synthetic peptides were used to address the fundamental problem of how HIV sequence variability affects T cell recognition. Even one conservative substitution can drastically reduce recognition; thus the interaction of gp120 epitopes with T cell receptors and MHC is precise and poorly crossreactive. Importantly, a subset of CD4+ gp120-specific clones manifest cytolytic activity and lyse uninfected autologous CD4+Ia+ T cells in the presence of gp120 in a process that is strictly dependent upon CD4-mediated uptake of gp120 by T cells. Assuming gp120 is shed from HIV-infected cells in vivo, this novel CD4-dependent autocytolytic mechanism may contribute to the profound depletion of CD4+ cells in AIDS.

The differentiation of O-2A progenitor cells into oligodendrocytes is associated with a loss of inducibility of Ia antigens

Current data suggest that some astrocytes, one of the 3 main types of macroglia in the central nervous system (CNS), can be induced by interferon-gamma (IFN-gamma) to express major histocompatibility complex class II antigens (immune-associated or Ia) and present antigen to T lymphocytes. In contrast, oligodendrocytes, another type of macroglia, cannot be induced to express Ia. The astrocytes which have been shown to express Ia are from a particular glial lineage and are called type-1 astrocytes. The oligodendrocyte-type-2 astrocyte (O-2A) lineage, which gives rise to oligodendrocytes, also gives rise to a second class of astrocytes called type-2 astrocytes and the ability of type-2 astrocytes or the common O-2A progenitor cell to express Ia is not known. We have now found that both type-2 astrocytes and O-2A progenitor cells can be induced to express Ia by IFN-gamma but Ia expression is not induced in oligodendrocytes in parallel cultures. Thus, it appears that differentiation of O-2A progenitor cells into oligodendrocytes is specifically associated with a loss of inducibility of Ia. This apparent loss of the capacity for Ia expression, and presumably antigen presentation, in oligodendrocytes (the cells which produce myelin in the CNS) is of particular interest in view of the ability of immunization of myelin components to produce autoimmune-mediated paralytic disease.

Expression of HLA-DR antigens on bile duct epithelium in primary sclerosing cholangitis

The expression of HLA class I (HLA-A, B, C) and class II (HLA-DR) antigens on the biliary epithelium of 10 patients (nine men) with primary sclerosing cholangitis (PSC) was investigated using an immunoperoxidase technique on cryostat sections. Five patients were staged as grade II and five grade III on hepatic histology. None were cirrhotic. as grade II and five grade III on hepatic histology. None were cirrhotic. Controls were nine patients with primary biliary cirrhosis (PBC), five with extra hepatic biliary obstruction, 15 with other forms of chronic liver disease and six with normal livers. Bile ducts from the normal subjects and patients with chronic liver disease did not express HLA-DR antigens. In contrast, all 10 of the PSC biopsies showed varying degrees of HLA-DR staining of the biliary epithelium. Expression of DR antigens was also found on the bile ducts of all five patients with extra hepatic biliary obstruction and in six of nine patients with PBC. Expression of HLA class I antigens was seen on the biliary epithelium of all the biopsies examined. Increased numbers of helper and suppressor T-cells were seen in the portal tracts of all the PSC patients. This study has confirmed that aberrant expression of HLA-DR may occur on the biliary epithelium of some, but not all, patients with PBC. In addition, the study has shown that aberrant expression of HLA-DR always occurs in PCS at an early stage of histological liver damage. While this may be important in the pathogenesis of PSC, the aberrant expression in extra hepatic biliary obstruction suggests that it may be a secondary phenomenon.

HLA-DR antigen expression on the thyrocytes of Graves' disease patients

To confirm the expression of HLA-DR antigen on the thyrocytes of Graves’ disease patients and study the relation between the degree of DR antigen expression and clinical or laboratory indices, double immunofluorescence and immunoenzymatic staining were performed on frozen thyroid sections. DR antigen was expressed on the thyrocytes of 8 of 11 patients with Graves’ disease (73%) but not found on the thyrocytes from 6 normal controls. The degree of DR antigen expression had no apparent correlation with the age, duration of the disease, activity of TBII, titers of antimicrosomal and antithyroglobulin antibody. There was no apparent spatial or quantitative relation between lymphoid follicle formation and the DR antigen expression on the thyroid follicles. But DR antigen tended to be expressed on the thyroid tissue with interstitial, lymphocyte infiltration. In conclusion, DR antigen was expressed on the thyrocytes of Graves’ disease patients but the clinical and immunological significance remains to be clarified.

Immunocytochemical analysis of HLA class II (DR) antigens in liver disease in man

The in situ distribution of the major histocompatibility (HLA) class II (DR) antigens was studied in 113 liver biopsy specimens and five livers obtained at necropsy, using monoclonal antibody CR3/43. In 20 normal livers HLA-DR antigens were not detected in bile duct epithelium, hepatocytes, or portal vein endothelium. Normal arteriolar, sinusoidal and central venous endothelium often expressed HLA-DR. Kupffer cells always expressed these antigens. HLA-DR positive spindle cells were identified in the connective tissue of portal tracts, large hepatic veins, and liver capsule: most shared antigens common to all leucocytes and reacted with the histiocytic maker EBM11. Bile duct epithelium expresses HLA-DR in primary biliary cirrhosis, large duct obstruction, and drug induced cholestasis, indicating that HLA-DR positive spindle cells are phenotypically similar to histiocytes.

Synthesis and cell surface display of class II determinants by long-term propagated rat T line cells

We have investigated the capacity of the encephalitogenic BS rat T cell line bs 83 and its variant clone bs 83.III.C6 to synthesize and express RT1.B-specific class II molecule subsets defined by monoclonal antibodies (mAb) MRC-OX6 and MRC-OX3. Earlier studies had indicated that mAb MRC-OX6 recognizes three distinct molecular species: an immature oligomeric polypeptide chain complex comprised of the polymorphic subunits alpha, beta and the invariant proteins of the gamma group; a biosynthetic intermediate composed of post-translationally modified alpha, beta and gamma chain (denoted p35) and a fully glycosylated alpha, beta two-chain complex derived from the plasma membrane. MRC-OX3 was shown to recognize a serologically distinct alpha, beta two-chain complex that coexists with the MRC-OX6-specific heterodimer at the cell surface. Here we show that premutant bs 83 cells were unable to synthesize class II molecules of either set. In contrast endogeneous synthesis by mutant cells of MRC-OX6-specific molecules was demonstrated. Unlike control spleen cells variant cells failed to synthesize the mature MRC-OX3-reactive class II subset. Instead a three-polypeptide chain complex comprised of the terminally glycosylated subunits alpha, beta and invariant chain p35 was present at the cell surface. This complex appears to represent the preserved biosynthetic intermediate that failed to release invariant chain p35 upon its transit into the plasma membrane. These latter observations support our notion of gamma chain-induced epitope diversification during post-translational maturation of RT1.B-specific class II molecules.

Increased percentage of activated Ia+ T lymphocytes in peripheral blood of neonates following exchange blood transfusion

The expression of Ia-like antigens in peripheral blood T lymphocytes from newborns receiving postnatal total blood exchange was analyzed. A significantly increased percentage of Ia-positive T lymphocytes (Ia+ T cells) was observed 2 days after postnatal transfusion with total blood in comparison to data observed on Days 0, 5, and 15. Ia+ T cells were also significantly higher than in normal control newborns tested in the same period. When newborns received the blood exchange with irradiated total blood or with leukocyte-depleted blood, no increase in Ia+ T cells was observed and the percentage of these cells remained in the normal range (1-7%) on all the days tested (0, 2, 5, 15 days). For easy identification of the origin of Ia+ T cells, sex-incompatible blood was used for exchange, and a karyotype analysis was carried out for the detection of the Y chromosome on Ia+ T cells separated from peripheral blood on Day 2 and then cultured with interleukin 2 (IL-2) for 48 hr. It was thus established that Ia+ T cells were not of donor origin. Simultaneously with the expression of Ia-like antigens, host T cells also carried the interleukin-2 receptor (TAC). An allogeneic response, comparable to a host-versus-graft reaction, was probably responsible for the activation of T cells 2 days after total blood exchange in newborns.

Immunologic classification of lymphoma and lymphoid leukemia

Important insights into lymphocyte differentiation and the cellular origins of lymphoma and lymphoid leukemia have been gained through the use of monoclonal antibodies that define cell surface antigens and molecular probes that identify immunoglobulin and T cell receptor genes. Results of these studies have been combined with markers such as surface membrane and cytoplasmic immunoglobulin on B lymphocytes, sheep erythrocyte receptors on T lymphocytes, and cytochemical stains. Utilising all of the above markers, it is now clear that acute lymphoblastic leukemia (ALL) is heterogeneous. Furthermore, monoclonal antibodies that identify B cells such as the anti-B1 and anti-B4 antibodies in combination with studies of immunoglobulin gene rearrangement have demonstrated that virtually all cases of non-T-ALL involve B lymphocytes. At least six distinct subgroups of non-T-ALL can now be identified. T-ALL is subdivided by the anti-Leu-9, anti-Leu-1, and additional antibodies that separate T lymphocyte subsets into three primary subgroups. Monoclonal antibodies are also useful in the subclassification of non-Hodgkin's lymphoma, and certain distinct markers can be correlated with morphologic classification.

Jejunal mucosa lymphoid cell subsets and the expression of major histocompatibility complex antigens in children

Using monoclonal antibodies with the immunoperoxidase technique the distribution pattern of class I and class II antigens of the major histocompatibility complex (MHC), and of the lymphocyte subsets have been studied in intestinal biopsies from children without mucosal lesions, from children with coeliac disease (CD) and from infants with cow's milk protein intolerance (CMPI). The staining of the intestinal mucosa for class I antigens is unaltered irrespective of the histological picture or the clinical diagnosis. Class II antigens are only partially or not expressed at all by epithelial cells in untreated coeliac disease and in some cases of cow's milk protein intolerance. The number and the composition of the lamina propria lymphocytes in both CD and CMPI are different from the normal situation. An increase of all lamina propria lymphocyte subsets is observed in untreated CD. A decrease of OKT4+ lymphocytes is observed in the lamina propria of CMPI patients. These changes may be involved in the pathogenesis of these diseases.

HLA-DR antigen expression on T cells from cerebrospinal fluid in multiple sclerosis and aseptic meningo-encephalitis

HLA-DR expression on T lymphocytes in cerebrospinal fluid (CSF) from patients with multiple sclerosis (MS) and acute aseptic meningo-encephalitis (AM), and from blood only from healthy controls was examined by a new double-immunofluorescence labelling assay using species-specific second layers on prefixed cell samples. Thirteen of 16 patients with AM (81%) had an elevated percentage of DR positive T cells in CSF against only two of 20 patients with MS (10%). Our data indicate that AM, an acute infection of the central nervous system (CNS), is accompanied by accumulation in CSF of activated, DR positive T cells as a reflection of actively involved cellular immunity within the CNS, while this accumulation of DR positive T cells is not seen in MS, a chronic inflammatory CNS disease, despite some of the patients being examined during clinical exacerbations.

Activation marker analysis of mononuclear cell infiltrates of oral lichen planus in situ

Monoclonal activation markers (Ia, Tac, T9, and 4F2) were used to detect the degree of activation of mononuclear cells in the inflammatory infiltrates of oral lichen planus in situ. In addition the specimens were stained with the following monoclonal antibodies: T4, T8, T11, M1, and pan-B. T-lymphocyte was the predominant cell type in the inflammatory infiltrates. According to the results of the activation marker analysis, the majority of the T-lymphocytes were resting. However, activated cytotoxic T8 and 4F2 T-cells were located close to damaged basal cells; this finding may suggest that they are responsible for the damage and supports the claim that a cell-mediated immune response participates actively in local pathogenetic mechanisms in oral lichen planus.

Increased circulating Ia-positive T cells in patients with idiopathic thrombocytopenic purpura

Peripheral blood T cells from 40 patients with idiopathic thrombocytopenic purpura (ITP) were analysed for the presence of surface Ia antigens using monoclonal antibodies by indirect immunofluorescence. The percentage of Ia-positive (Ia+) T cells was significantly increased in patients with ITP (6.8 +/- 2.9%, P less than 0.005) as compared with normal controls (2.3 +/- 0.9%). There was an inverse correlation between the percentages of Ia+ T cells and platelet counts (r = 0.58, P less than 0.005) and a positive correlation between the percentage of these cells and platelet-associated IgG (PAIgG) values (r = 0.55, P less than 0.01). The percentage of Ia+ T cells was found to decrease within two weeks during therapy with high dose gamma-globulin or corticosteroid. We have previously reported the presence of T cells bearing both helper/inducer (H/I) and suppressor/cytotoxic (S/C) phenotypes (double labelled cells, DLC) in patients with ITP and an inverse correlation between the percentages of DLC and their platelet counts. In the present study, we showed that a major part of Ia+ T cells had both H/I and S/C phenotypes. We also examined the correlation between Ia+ T cells and autologous mixed lymphocyte reaction (AMLR). A defective AMLR was demonstrated in patients with ITP. Furthermore, an inverse correlation was found between the percentages of Ia+ T cells and the proliferative responses to AMLR (r = -0.49, P less than 0.01). These results suggest that increased circulating Ia+ T cells play a role in the abnormalities of the immunoregulatory system of ITP, especially in the regulation of autoantibody production.

Co-expression of CD4 and CD8 molecules and de novo expression of MHC class II antigens on activated rat T cells

Rat T-cell populations were analysed for their surface expression of CD4, CD8 and class II MHC antigens using monoclonal antibodies (McAbs) W3/25, Ox8 and Ox6 in immunofluorescence and immunoenzyme cytochemistry. Resting T cells expressed either CD4 (W3/25) or CD8 (Ox8) molecules, but not both, and did not express class II MHC antigens. In contrast, when purified T cells were stimulated by Con A or by alloantigens in a mixed lymphocyte reaction (MLR), over 60% of the cells expressed class II MHC antigens after 48-72 hr. The expression of class II MHC antigens by the T-cell blasts was transient and no longer evident after 96 hr of activation. In addition, T cells activated by either alloantigen or lectin expressed CD4 (W3/25) and CD8 (Ox8) molecules simultaneously: 30% of cells activated in MLR and 50% of Con A-activated cells expressed both markers within 48 hr of activation. The overlapping of the CD4- and CD8-positive subpopulations within the T-cell population was inferred from the results of staining for each marker separately and confirmed using a double-immunoenzyme staining method.

Suppressor-cell dysfunction in children with histiocytosis-X

Suppressor-cell activity of peripheral blood mononuclear cells were examined and lymphocyte subsets analyzed in children with histiocytosis-X and in healthy, age-matched subjects. Suppressor-cell function was assessed by two methods, the indomethacin stimulation of mitogen-activated cultures and the concanavalin A-inducible suppressor-cell assay. The results of these two assays indicate that children with active disease have significantly decreased suppressor-cell activity. Additionally, the percentage and absolute number of OKT8+ lymphocytes were decreased in children with active disease. Suppressor-cell activity and lymphocyte subsets returned to normal, baseline levels with disease remission. This study documents for the first time suppressor-cell dysfunction and supports previous investigations in which suppressor T lymphocytes are deficient in children with active disease. These findings may explain certain clinical manifestations seen in children with histiocytosis-X.