Analysis of the processing of Plasmodium falciparum rhoptry-associated protein 1 and localization of Pr86 to schizont rhoptries and p67 to free merozoites

The processing and localization of Plasmodium falciparum rhoptry-associated protein 1 (RAP-1) products were examined using polyclonal and monoclonal antibodies raised to a recombinant protein containing residues 1-294 of RAP-1. Immunoblot and epitope mapping results with antibodies that selectively bound epitopes in the RAP-1 products Pr86, p82, and p67 showed that p82 and p67 are formed from Pr86 by progressive removal of epitopes from the amino-terminus of the RAP-1 coding sequence. The capacity of Pr86 to form complexes was revealed after size fractionation of parasite proteins radiolabeled in the presence of brefeldin A to prevent processing of Pr86. Fractions containing complexed Pr86 also contained the RAP-2 product p39 and the RAP-3 product p37, suggesting that Pr86, p39 and p37 may form complexes similar to complexes previously reported for p82 and p67 with p39 or p37. Immunofluorescence localization and immunoblot studies revealed that Pr86 is present in the rhoptries, but only transiently, and that it is not detected in segmenting schizonts or extracellular merozoites. p67 and p82, on the other hand, were shown to be major RAP-1 components in purified merozoites. Neither p67 nor p82 were relocalized from the intracellular rhoptries to the merozoite surface under conditions that promoted relocalization of the rhoptry protein PF83/apical membrane antigen 1. These results suggest that processing of Pr86 begins after Pr86 complexes are transported to the forming rhoptries and that two site-selective processing reactions occur in the rhoptries, a rapid cleavage of Pr86 to p82 and a delayed cleavage of p82 to p67. Since p67 is missing from ring-stage parasites (Howard et al., Am J Trop Med Hyg, 1984;33:1055 59), the present results indicate there is a narrow time during which p67 may play a role in merozoite invasion of erythrocytes.

Functional analysis of the TCR alpha- beta+ cells that accumulate in the pneumonic lung of influenza virus-infected TCR-alpha-/- mice

In mice homozygous (-/-) for a targeted TCR-alpha gene disruption, some thymocytes express a cell-surface TCR-beta chain on the cell surface in the absence of a TCR-alpha chain, and a few CD4+CD8- TCR-alpha-beta+ cells accumulate in the peripheral lymphoid organs. We have infected these mutant mice with an influenza A virus to show that large numbers of TCR-beta+ cells (most of which are CD4+) can be retrieved from the pneumonic lung. Both freshly isolated TCR-alpha-beta+ cells and TCR-alpha-beta+ hybridoma cell lines derived from influenza virus-infected mutant mice respond appropriately to stimulation with anti-CD3 epsilon or the Mls-1 superantigen. It thus seems that CD4+ TCR-alpha-beta+ cells in the peripheral lymphoid organs of TCR-alpha mutant mice can signal through their TCR surface complex. However, there are no indications that CD4+ TCR-alpha-beta+ lymphocytes can either recognize a complex between MHC and influenza virus peptide or act as effector or Th cells. The existence and function of such cells in wild-type mice remains to be established.

Functional analysis of the TCR alpha- beta+ cells that accumulate in the pneumonic lung of influenza virus-infected TCR-alpha-/- mice

In mice homozygous (-/-) for a targeted TCR-alpha gene disruption, some thymocytes express a cell-surface TCR-beta chain on the cell surface in the absence of a TCR-alpha chain, and a few CD4+CD8- TCR-alpha-beta+ cells accumulate in the peripheral lymphoid organs. We have infected these mutant mice with an influenza A virus to show that large numbers of TCR-beta+ cells (most of which are CD4+) can be retrieved from the pneumonic lung. Both freshly isolated TCR-alpha-beta+ cells and TCR-alpha-beta+ hybridoma cell lines derived from influenza virus-infected mutant mice respond appropriately to stimulation with anti-CD3 epsilon or the Mls-1 superantigen. It thus seems that CD4+ TCR-alpha-beta+ cells in the peripheral lymphoid organs of TCR-alpha mutant mice can signal through their TCR surface complex. However, there are no indications that CD4+ TCR-alpha-beta+ lymphocytes can either recognize a complex between MHC and influenza virus peptide or act as effector or Th cells. The existence and function of such cells in wild-type mice remains to be established.

Human monoclonal antibodies against Plasmodium falciparum: production, stabilization and characterization

Nine human monoclonal antibodies (MoAbs) recognizing 7 different antigenic structures of blood-stages of the human malarial parasite P. falciparum (Pf) were produced by Epstein-Barr virus transformed B-cell lines (EBV-TCL) with or without fusion to the lymphoblastoid cell line KR4. The peripheral blood B-lymphocytes were obtained from 8 Gambian donors immune to Pf malaria. Two of the EBV-TCL could be expanded and maintained for more than 6 months but neither one could be cloned. Six additional EBV-TCL were stabilized after fusion with the KR4 lymphoblastoid cell line. All resulting hybridomas permitted easy cloning. Some of the MoAbs produced distinct fluorescent staining patterns of asexual Pf blood-stage parasites when using high-resolution digitized video-intensified fluorescence microscopy. Antigens on 195 kD and 155 kD proteins were recognized by 3 and 1 MoAb, respectively, using Western blotting and immunoprecipitation techniques.

Adolescent residential treatment: a one to three year follow-up

Considerable difficulties have been encountered in the residential treatment of adolescents with psychiatric disorders. Few of these programs have been successful. This study describes the long term effectiveness of a residential treatment program for disturbed adolescents. This program was particularly successful in returning severely disturbed adolescents to the community. None of the adolescents needed intensive residential treatment during the follow-up period. Three objective measures (Global Assessment Scale, Level of Functioning Scale, Adolescent Functioning Scale) were used at three specific times (admission, discharge and long term follow-up) to determine the level of psychosocial functioning of each adolescent. A significant improvement was found in the adolescents' level of functioning. These treatment gains were maintained at the time of long term follow-up (one to three years).

The role of the T cell receptor in positive and negative selection of developing T cells

Although many combinations of alpha beta T cell receptors are available to the T cells in any given organism, far fewer are actually used by mature T cells. The combinations used are limited by two selective processes, positive selection of T cells bearing receptors that will be useful to the host, and clonal elimination or inactivation of T cells bearing receptors that will be damaging to the host. The ways in which these two apparently contradictory processes occur, and the hypotheses that have been suggested to reconcile them, are discussed.

The effects of Plasmodium falciparum malaria on immune control of B lymphocytes in Gambian children

Children living in hyperendemic malarious regions have high immunoglobulin levels and an increased frequency of Burkitt's lymphoma. In a study of Gambian children which endeavours to explain these findings we showed that acute P. falciparum malaria caused spontaneous activation and growth of their B lymphocytes in vitro. A high proportion of these cells contained Epstein-Barr nuclear antigen (EBNA). In ancillary experiments aimed at explaining these findings. CD4 helper cells from adult donors were destroyed with monoclonal antibody and complement. This manoeuvre resulted in loss of cytotoxic T cell control of their B lymphocytes when infected with Epstein-Barr virus (EBV). In children with acute malaria, both spontaneous immunoglobulin and antibody production by B cells was increased yet CD4 helper cell control over these cells, as measured by responses to pokeweed mitogen, was found to be intact. Spontaneous and concanavalin A-driven lymphocyte proliferation was depressed. We infer from these findings that in patients with P. falciparum malaria loss of cytotoxic T cell control of the EBV in B cells, possibly due to destruction or dysfunction of a subset of CD4 cells responsible for induction of suppressor/cytotoxic CD8 cells, leads to activation and proliferation of foci of B cells containing EBV. The expanded pool and rapid turnover of these cells may increase chances of malignant transformation leading to the genesis of Burkitt's tumor. Partial loss of suppressor mechanisms coupled with normal CD4 helper/inducer activity may result in high serum levels of immunoglobulin which are characteristic of persons living in malarious regions.

The toxicity of staphylococcal enterotoxin B in mice is mediated by T cells

Staphylococcal enterotoxin B (SEB) has been shown in the past to be a potent T cell stimulant in mouse or man. The toxin acts as a superantigen that is, it binds to class II MHC proteins and, as such a complex, stimulates T cells bearing particular V beta s as part of their receptors. The toxin also has several pathological effects, causing, in mice, rapid weight loss, thymus atrophy, immunosuppression, and, at high doses, death. The data in this paper show that at least one of these effects, weight loss, is T cell mediated. Staphylococcal enterotoxin-mediated weight loss is MHC dependent, and is almost absent in animals expressing MHC class II molecules, which, complexed with SEB, are poor T cell stimulants. Also, mice that lack T cell function, genetically or because of cyclosporin A treatment, lose no or less weight than controls in response to SEB. Finally, animals bred such that they express few T cells bearing V beta s with which SEB can interact lose much less weight in response to the toxin than littermate controls that have higher numbers of reactive T cells. It is therefore suggested that the pathological effects of the staphylococcal, T cell-stimulating toxins in mouse and man may be partially or wholly the consequence of massive T cell stimulation.

Plasmodium falciparum schizont sonic extracts suppress lymphoproliferative responses to mitogens and antigens in malaria-immune adults

Cellular immune responses to malaria antigens are suppressed during acute Plasmodium falciparum infection, and evidence from both murine and human studies suggests that parasite-derived factors may be directly immunosuppressive. In this study we have shown that P. falciparum schizont sonic extract will suppress in vitro lymphoproliferative responses to purified malaria antigens and other soluble antigens. The degree of suppression appears to correlate with the level of the lymphoproliferative response to the schizont preparation and is correspondingly more marked in malaria-immune donors than in nonimmune individuals. The effect can be transferred with primed mononuclear cells and is partially abrogated by removal of CD8+ lymphocytes. The suppressive component of the schizont preparation is nondialyzable and partially heat labile and comigrates with hemoglobin-derived proteins in the molecular mass range 10 to 20 kilodaltons.

Two better cell lines for making hybridomas expressing specific T cell receptors

Two variants of the AKR thymoma BW5147 have been isolated which can no longer express functional TCR alpha- and beta-chains. By generating hybridomas with these variant fusion lines, TCR of any normal T lymphocyte, including TCR-gamma/delta, can be studied at a clonal level, without interference of the BW5147-derived receptor chains. In this study one of the variants has been useful in identifying the reactivity to allogeneic MHC Ag of BW5147 itself.

Two better cell lines for making hybridomas expressing specific T cell receptors

Two variants of the AKR thymoma BW5147 have been isolated which can no longer express functional TCR alpha- and beta-chains. By generating hybridomas with these variant fusion lines, TCR of any normal T lymphocyte, including TCR-gamma/delta, can be studied at a clonal level, without interference of the BW5147-derived receptor chains. In this study one of the variants has been useful in identifying the reactivity to allogeneic MHC Ag of BW5147 itself.

The structure of V alpha and J alpha segments in the mouse

Antigen receptors on most T-cells are heterodimeric glycoproteins, comprised of an alpha chain and a beta chain. These chains are encoded by discontiguous variable (V), diversity (D) and joining (J) gene segments that rearrange to produce a contiguous and functional alpha or beta chain gene. To investigate the size and diversity of the germline repertoire of alpha-chain gene segments, we have characterized and sequenced 20 alpha chain cDNAs. Among these cDNA clones, we have found 4 J alpha and 4 V alpha sequences that have not yet been described. The relationship of these "new" gene segments to those already characterized is discussed.

A case of mistaken identity: a fourth ventricular tumor presenting as school phobia in a 12 year old boy

A 12 year old boy was diagnosed as having overanxious disorder of childhood and school phobia. He was later found to be suffering from the effects of a cerebral tumor. Surgical removal of the tumor led to alleviation of the anxiety. The authors utilize this case to illustrate some aspects of differential diagnosis in child psychiatry. In particular, they point out the necessity of comprehensive physical examination in child psychiatry impatient units. The danger of attributing physical symptoms to functional illness purely in the absence of positive physical findings is noted. The importance of utilizing a biopsychosocial diagnostic model in child psychiatry is stressed.

A T cell receptor V beta segment that imparts reactivity to a class II major histocompatibility complex product

We have identified in mice an allele of a new T cell receptor V beta gene, V beta 17a, whose product is bound by the monoclonal antibody KJ23a. Over 90% of T cell hybridomas prepared from V beta 17a+ T cells of SWR mice respond to allogeneic forms of the IE class II MHC protein, indicating that V beta 17a has an appreciable affinity for IE regardless of the other components of the T cell receptor. These results suggest a bias in the germ-line T cell receptor repertoire toward recognition of MHC proteins and indicate that the V beta portion of the receptor may form the most important contact points with MHC ligands.

Infection of cultured murine brain cells by Semliki Forest virus: effects of interferon-alpha beta on viral replication, viral antigen display, major histocompatibility complex antigen display and lysis by cytotoxic T lymphocytes

Primary brain cell cultures prepared from newborn mice were infected with Semliki Forest virus (SFV). The effects of interferon (IFN-alpha beta) treatment on SFV replication, SFV and major histocompatibility complex (MHC) class I antigen expression, and susceptibility to lysis by SFV-specific cytotoxic T lymphocytes (CTL) were determined. The IFN-alpha beta treatment prevented replication of SFV as determined by incorporation of [3H]uridine into SFV RNA and very markedly reduced the expression of SFV antigens on the cell surface as determined by lysis with antibody and complement or indirect immunofluorescence. However, IFN-alpha beta increased expression of MHC class I antigens, measured by indirect immunofluorescence and as assessed indirectly by susceptibility to killing by alloreactive T cell lines. SFV infection had no effect on MHC class I expression in either IFN-alpha beta-treated or -untreated cells. The infected IFN-alpha beta-untreated brain cells were susceptible to killing by the CTL at effector/target ratios in the range 3 to 30. The killing was MHC antigen-restricted, and uninfected cells were not killed. A target cell (YAC) highly susceptible to natural killer cell cytotoxicity was not killed by the CTL. IFN-alpha beta treatment prior to SFV infection resulted in an augmentation of lysis by the CTL, indicating that even where SFV antigen expression is reduced, in the context of enhanced MHC class I expression brain cells remain susceptible to CTL killing.

The T cell repertoire may be biased in favor of MHC recognition

The receptors of two T cell hybridomas that recognize class I and class II major histocompatibility complex (MHC) molecules, respectively, have been compared. In both cases these receptors are hybrid molecules formed as a result of cellular fusion. The receptors contain the same alpha chain, contributed by the tumor cell fusion partner, and related beta chains, contributed by the normal T cell component. Thus, surprisingly, the same alpha chain can contribute to recognition of class I and class II MHC molecules. Moreover, the finding that in two independent examples hybrid receptor molecules created randomly by in vitro cell fusion recognize MHC supports the theory that the T cell repertoire has an intrinsic affinity for MHC.

A preliminary outcome study of a community group treatment programme for emotionally disturbed adolescents

The treatment of adolescents with psychiatric disturbance remains a highly unsuccessful area. Empirical research is limited and treatment decisions are often based on theoretical bias rather than proven results. This study reports on the results of a multivariate analysis of pre- and post-individual and family measures on patients in a community based day and evening programme. The programme utilized a broad range of treatment modalities including group and family therapy and chemotherapy. An accredited educational programme was also provided to the patients attending the day programme. The results of this study showed that adolescents were referred to either the day or evening programme components based on level of acting out behaviour rather than on DSM III diagnosis. Adolescents reported significant positive changes at post testing in all areas, but this improvement was not endorsed by parents. Although therapists perceived considerable improvement in their families after treatment, this improvement did not show up on the family assessment measure chosen. The findings of the study endorse the need for further empirical research in adolescent treatment and underscores the fallacy of relying on anecdotal evidence to report treatment results. Questions are raised as to the operational usefulness of the present DSM III criteria in making treatment decisions and the validity of associating individual dysfunction with family dysfunction. Some question as to the sensitivity of the family measure used was also raised. The study outlined strengths and weaknesses in the present treatment programme and underscored the importance of further evaluative research, if the treatment of adolescents with psychiatric disturbance is to become successful.

The interaction of interferon with the immune response

Interferon (IFN) is a component of the immune response and influences immune responses as demonstrated by in vitro experimentation. In this review these complementary aspects of IFN's interaction with the immune response are discussed. Of chief interest is IFN-gamma ('immune' IFN) but IFNs-alpha and -beta are also considered.