Antigen-specific human T lymphocyte clones: induction, antigen specificity, and MHC restriction of influenza virus-immune clones

Human peripheral blood lymphocytes from an HLA-Dw1,3 individual were primed in vitro with influenza A virus (A/Texas/1-77/x-49) and subsequently cloned by limiting dilution in TCGF. Of the 96 TLCs originally obtained, nine were characterized in detail. TLCs were antigen specific, responding to influenza A virus, not to influenza B, TGAL, GAT, tetanus toxoid, or KLH, and only when antigen was presented by cells unable to form rosettes with AET-treated SRBC. Presentation of antigen by unseparated PBL often resulted in significant "back stimulation," probably via production of growth factors. The MHC requirements for the induction of TLC proliferation were analyzed. Of four representative clones analyzed, three required Dw1;DR1 compatibility for successful presentation of viral antigens by a panel of antigen-presenting cells. In contrast, one TLC showed an unusual pattern of response that could not be correlated to a particular HLA haplotype. Monoclonal anti-T cell antibody analysis of the surface phenotype of two TLCs maintained in continuous culture for 5 mo indicated that they were OKT3+, 4+, and 8-, consistent with an inducer/helper phenotype. To confirm the clonal nature of TLCs, data on the functional properties of TLC subclones are also presented.     

A study of the functional capabilities of human neonatal lymphocytes for in vitro specific antibody production

The ability of neonatal B and T cells to participate in the in vitro production of anti-influenza virus antibody was studied. Peripheral blood mononuclear cells from nearly all normal adults produce anti-influenza virus antibody when stimulated in vitro with type A influenza virus. Cord blood mononuclear cells, however, consistently failed to do so. Using Epstein-Barr virus activation or coculture with irradiated adult T cells in the presence of influenza virus to identify precursor B cells for anti-viral antibody production, newborns were found to have a decreased number of influenza-specific B cells as compared with adults. Thus, a paucity of precursor B cells for anti-influenza virus antibody was one factor contributing to the absent in vitro antibody response. Additional studies were undertaken to investigate the capabilities of newborn T cells in the in vitro response to influenza virus. Newborn T cells failed to proliferate when cultured with influenza virus. Irradiated newborn T cells were, however, able to provide help for specific antibody production in influenza virus-stimulated cocultures with allogeneic adult B cells, and newborn T cells proliferated when stimulated with alloantigens; their helper function in allogeneic coculture was, thus, likely mediated by T cells stimulated by alloantigens rather than by influenza virus. In the absence of T cell irradiation, no antibody was produced in cocultures of adult B cells and neonatal T cells, at least in part as the result of a radiosensitive suppressor T cell. Suppression in influenza virus-stimulated allogeneic cocultures was also observed with normal adult T cells and is, therefore, a property of both newborn and adult T cells. Thus, allogeneic help and suppression can both be manifested in exogenous antigen-stimulated allogeneic cocultures. In addition, both of these allogeneic effects can be mediated by neonatal T cells, indicating that these functions are present at the time of birth and do not require previous exogenous antigenic exposure for expression.     

Human peripheral blood mononuclear cells produce IgA anti-influenza virus antibody in a secondary in vitro antibody response

The function and immunoregulation of human IgA memory B cells producing anti-influenza virus antibody was analyzed in vitro in antigen-stimulated cultures. Peripheral blood mononuclear cells (PBMC) from seven of eight normal adult volunteers naturally immunized to influenza virus produced IgA anti-influenza virus antibody when stimulated in vitro with inactivated A/Aichi/68 [H3N2] influenza virus. This IgA antibody response was approximately one-eighth the IgG antibody response. PBMC from each of five patients with selective IgA deficiency failed to produce any measurable IgA antibody. When tonsillar mononuclear cells (TMC) were studied in a similar manner, a relatively higher IgA antibody response was obtained (one-third the IgG antibody) than with PBMC. Additional studies were undertaken to investigate the immunoregulation of this IgA antibody production and the relatively lower amount produced by PBMC than by TMC. Co-cultures of peripheral blood B cells with irradiated peripheral blood T cells (to possibly inactivate a radiosensitive IgA suppressor cell) did not result in a relative increase in IgA antibody production. Also, co-cultures of B cells with increasing numbers of T cells produced parallel increases of IgG and IgA antibody when plotted on a log scale with slopes of approximately 1, suggesting that a single helper T cell was limiting for both isotypes. Finally, pokeweed mitogen-stimulated co-cultures of peripheral blood and tonsillar B and T cells revealed that the B cell population, but not the T cell population, determined the amount of IgA anti-influenza virus antibody produced. Precursor frequency analyses of tonsillar and peripheral blood B cells in antigen-stimulated cultures confirmed that tonsils contained a higher precursor frequency of B cells for IgA anti-influenza virus antibody production (3.95/10(6) B cells) than did peripheral blood B cells (0.65/10(6) B cells). Thus, IgA memory cells are preferentially found in tonsillar tissue as compared with the peripheral blood, consistent with the role of the tonsils as a mucosal immune organ.     

Role of the LFA-1 molecule in cellular interactions required for antibody production in humans

The lymphocyte function-associated antigen 1 (LFA-1) has been shown to play a role in various T cell functions in mice and humans including cytotoxicity, and proliferation to allogeneic cells and foreign antigens. These functions have been defined with specific monoclonal antibodies and were additionally confirmed by the investigation of patients with inherited deficiency in membrane LFA-1 expression. In this paper, we report our studies on the potential role of the LFA-1 molecule in T lymphocyte-dependent antibody responses. In a patient with a complete lack of membrane expression of LFA-1, there was no in vivo antibody response to vaccinal antigens such as tetanus, diphtheria toxoids, and polio virus, and no in vivo or in vitro antibody production to influenza virus, whereas serum immunoglobulin levels and antibodies to polysaccharides (isohemagglutinins, antibody to mannan, and a polysaccharide from Candida albicans) were detected in correlation with in vitro production of anti-mannan antibody. The defective antibody response to polypeptides was not secondary to poor antigen-specific T proliferation, because the latter was found to be present. Similarly, in vitro antibody production to influenza virus of normal cells was blocked by several anti LFA-1 monoclonal antibodies specific for the alpha subunit of the molecule, if they were added from the beginning of the culture. The antibody production blockade could be achieved with monoclonal antibody concentrations that partially preserved T cell proliferation. The helper effect of an influenza virus-specific helper T cell clone was also blocked. The targets of the blockade were shown by incubation experiments to be T cells and monocytes. In contrast, anti-LFA-1 monoclonal antibodies had no effect on pokeweed mitogen-induced B cell maturation into immunoglobulin-containing cells and on the anti-mannan antibody production. These combined data demonstrate that the LFA-1 molecule plays a role in T cell dependent antibody production to polypeptidic antigens but not in the antibody response to polysaccharides, although the antibody response to mannan is T cell dependent. It is proposed that the LFA-1 molecule is required to some extent for a antigen-presenting cells-T lymphocyte interaction and for the maintenance of a close association between antigen-specific helper T cells and small resting B lymphocytes. Polysaccharidic antigens that exhibit repetitive antigenic determinants might cross-link membrane immunoglobulins on B lymphocytes, thus allowing B cells to pass through a first step of activation requiring cognate T-B cell interaction.     

Regulation of influenza virus-specific cytotoxic T cell responses by monoclonal antibody to a human T cell differentiation antigen

The results in this report indicate that the OKT3 monoclonal antibody, which is specific for a human T cell differentiation antigen present on 90 to 95% of peripheral T cells, can exert several effects that regulate the generation and expression of human influenza virus-immune cytotoxic T lymphocytes (CTL). The OKT3 antibody, but not OKT1 or OKT11 (which bind to all peripheral T cells), is able to inhibit anti-influenza CTL effector cell activity. An F(ab')2 preparation of OKT3 IgG were as effective as whole IgG for the inhibition of CTL effectors, indicating that the inhibitory activity of the antibody was not a function of the Fc portion of the molecule. OKT3 IgG and OKT3 F(ab')2 fragments (but not OKT4, OKT8, or OKI were able to inhibit the generation of anti-influenza CTL. The culture of human lymphoid cells with OKT3 in the presence or absence of influenza virus induced radioresistant cells that could suppress the CTL response of fresh autologous lymphocytes to influenza. These results suggest that T cell functions can be regulated by signals that are initiated by the binding of antibody to cell surface molecules that may not be related to the T cell antigen-specific receptor(s).     

Cytolytic T lymphocyte and antibody responses to synthetic peptides of influenza virus hemagglutinin

Two peptides corresponding to HA1(181-204) and HA2(103-123) of the A/Japan/305/57 influenza virus hemagglutinin (HA) were chemically synthesized by solid-phase methods and were tested for their ability to generate murine secondary anti-influenza cytolytic T lymphocytes (CTL) in vitro and to bind monoclonal anti-HA antibodies. Peptide HA1(181-204) could only generate CTL in the presence of helper factors contained in supernatant fluids from either Concanavalin A-stimulated mouse spleen cultures or WEHI-3 cells grown in vitro. Peptide HA2(103-123) stimulated the induction of anti-influenza CTL independent of helper factors, but the stimulation was also greatly increased if helper factors were added. A 10-fold molar excess of peptide HA2(103-123) was required to obtain optimal CTL activation over the quantities required in the HA1(181-204) system. This molar ratio remained unchanged, even in the presence of helper factors. Induction of influenza-specific CTL was antigen-dependent in both systems, even though some killing of noninfected target cells was also occasionally observed. Our results suggest that synthetic peptides can be recognized as antigenic determinants in the generation of H-2-restricted anti-viral CTL capable of killing appropriately infected target cells. The inability of peptide HA1(181-204) to generate sufficient help for CTL development suggests that certain regions of the HA can be recognized by CTL precursors, but not by all of the required helper cells. Peptide HA1(181-204) also reacted with three monoclonal anti-HA antibodies as well as mouse anti-influenza (A/Japan/305/57) immune sera. This antibody reactivity suggests the possibility of a shared antigenic epitope or region between T and B cells, and therefore provides new insight in our understanding of viral antigenicity.     

Mechanisms of augmented resistance of cyclosporin A-treated mice to influenza virus infection by trehalose-6,6'-dimycolate.

Cyclosporin A (CsA), which is an immunosuppressive drug of helper T lymphocytes, diminished a resistance of mice to influenza virus infection. Mice inoculated intravenously with trehalose-6,6'-dimycolate (TDM, a glycolipid component of the cell wall of Mycobacterium) in an oil-in-water emulsion (TDM emulsion) recovered the resistance to influenza virus infection impaired by CsA. Number of antibody-producing cells was markedly reduced in CsA- and/or TDM-treated mice. Interferon production in lung of TDM-treated mice was augmented; however, it was extremely reduced not only in CsA-treated mice, but also in CsA- and TDM-treated mice. Activities of natural killer cells of CsA- and/or TDM-treated mice were not different from that of control mice. Numbers of lymphocytes in lung of TDM-treated mice and CsA- and TDM-treated mice were more predominantly increased than that of control mice. Analysis of lung lymphocytes by flow cytometry revealed no difference between the populations of L3T4+ T lymphocytes and Lyt-2.2+ T lymphocytes in CsA- and/or TDM-treated mice and the populations in control mice. However, the population of gamma delta T cell receptor positive (gamma delta TCR+) lymphocytes increased markedly in lung of TDM-treated mice and also CsA- and TDM-treated mice. In vitro experiments showed that macrophage cultures treated with TDM emulsion released a mediator(s) which activates T lymphocytes, but not B lymphocytes. These and our earlier results suggest that the recovered anti-influenza virus resistance of CsA-treated mice by treatment with TDM emulsion was caused by elicitation of macrophages with TDM, then activation of T lymphocytes, especially gamma delta TCR+ lymphocytes.     

Effects of Clinacanthus siamensis leaf extract on influenza virus infection

Ethanolic extracts of 20 medicinal plants were screened for influenza virus NA inhibition and in vitro antiviral activities using MDCK cells in an MTT assay. The vaccine proteins of influenza virus A/New Caledonia/20/99 (H1N1), mouse-adapted influenza virus A/Guizhou/54/89 (A/G)(H3N2) and mouse-adapted influenza virus B/Ibaraki/2/85 (B/I) were used in the NA inhibition assay, and mouse-adapted influenza viruses A/PR/8/34 (H1N1), A/G and B/I were used in the in vitro antiviral assay. The results of the in vitro antiviral assay indicated that the A/G virus was the most susceptible and an extract of the leaf of CS possessed the highest in vitro anti-A/G virus activity (41.98%). Therefore, the A/G virus and the CS extract were selected for studying in vivo anti-influenza virus activity. BALB/c mice were treated with CS extract (100 mg/kg per day, 5 times) orally from 4 hr before to 4 days after infection. CS extract elicited significant production of anti-influenza virus IgG₁ antibody in BAW and increased mouse weight compared to oseltamivir (0.1 mg/kg per day) on day 19 or water on days 17–19 of infection. Moreover, CS extract produced a higher anti-influenza virus IgA antibody level in BAW compared to oseltamivir, and a tendency towards an increase in anti-influenza virus IgA compared to water was shown. The results suggest that CS extract has a protective effect against influenza virus infection.     

Functional and molecular analysis of three distinct HLA-DR4 beta-chains responsible for the MLR between HLA-Dw4, Dw15, and DKT2

Differences in structure and function of HLA-class II molecules between HLA-DR4-related HLA-D specificities HLA-Dw4, Dw15, and DKT2 were investigated. Anti-HLA-DR framework monoclonal antibody HU-4 completely inhibited the one-way mixed lymphocyte reaction (MLR) between these specificities. HU-4 precipitated a monomorphic alpha-chain and a polymorphic beta-chain of human class II molecules from each B lymphoblastoid cell line (BLCL) homozygous for these three HLA-D specificities. We established IL 2-dependent T cell lines specific for streptococcal cell wall (SCW) antigen from peripheral blood lymphocytes (PBL) from four DR4-positive donors: an HLA-Dw4/DKT2 heterozygote, an HLA-Dw4/Dw12 heterozygote, an HLA-DKT2/D-blank heterozygote, and an HLA-Dw15/D-blank heterozygote. These T cell lines showed a proliferative response to SCW antigen in the presence of autologous or allogeneic antigen-presenting cells (APC) when T cell donors and APC donors shared at least one of the HLA-D specificities. This cooperation between the T cell line and APC was completely blocked by HU-4. We conclude from these data that the T cells could distinguish three distinct DR4 molecules expressed on APC of HLA-Dw4, Dw15, and DKT2 as restriction molecules at the presentation of SCW antigen.     

Generation of specific helper cells and suppressor cells in vitro for the IgE and IgG antibody responses.

Normal splenic lymphocytes from BDF1 mice were cultured on ovalbumin (OA)-bearing syngeneic peritoneal adherent cells for 5 days and their subsequent helper function was tested by an adoptive transfer technique. Lymphocytes harvested from the culture were mixed with DNP-KLH-primed spleen cells and transferred into irradiated syngeneic mice followed by challenge with DNP-OA. The results showed that the cultured lymphocytes has helper function for both IgE and IgG anti-DNP antibody responses. Depletion of mast cells and T cells in the peritoneal adherent cell preparations did not affect the generation of helper cells in the culture. The helper function of the cultured lymphocytes was abolished by the treatment with anti-theta antiserum and complement and was specific for ovalbumin. The OA-specific helper T cells were generated in vitro by the culture of a T cell-rich fraction of normal spleen on T cell-depleted OA-bearing peritoneal cells. If the normal splenic lymphocytes or T cell-rich fraction were cultured with 10 mug/ml of OA in the absence of macrophages, cultured lymphocytes lacked helper function. The transfer of splenic lymphocytes or splenic T cells cultured with soluble OA to normal non-irradiated mice, however, suppressed both IgG and IgE antibody responses of the recipients to subsequent immunization with DNP-OA. The suppressor cells were sensitive to anti-theta antiserum and complement and their activity was specific for OA. The cultured cells transferred into normal mice did not suppress anti-hapten antibody response to DNP-KLH. Normal lymphocytes cultured on OA-bearing macrophages and had helper function in adoptive transfer experiments failed to suppress antibody response of non-irradiated recipients to DNP-OA. The results indicate that OA-bearing macrophages primed T cells and generated helper T cells, whereas the culture of normal lymphocytes with soluble OA in the absence of macrophages generated suppressor T cells.     

Host differences in influenza-specific CD4 T cell and B cell responses are modulated by viral strain and route of immunization

The antibody response to influenza infection is largely dependent on CD4 T cell help for B cells. Cognate signals and secreted factors provided by CD4 T cells drive B cell activation and regulate antibody isotype switching for optimal antiviral activity. Recently, we analyzed HLA-DR1 transgenic (DR1) mice and C57BL/10 (B10) mice after infection with influenza virus A/New Caledonia/20/99 (NC) and defined epitopes recognized by virus-specific CD4 T cells. Using this information in the current study, we demonstrate that the pattern of secretion of IL-2, IFN-γ, and IL-4 by CD4 T cells activated by NC infection is largely independent of epitope specificity and the magnitude of the epitope-specific response. Interestingly, however, the characteristics of the virus-specific CD4 T cell and the B cell response to NC infection differed in DR1 and B10 mice. The response in B10 mice featured predominantly IFN-γ-secreting CD4 T cells and strong IgG2b/IgG2c production. In contrast, in DR1 mice most CD4 T cells secreted IL-2 and IgG production was IgG1-biased. Infection of DR1 mice with influenza PR8 generated a response that was comparable to that in B10 mice, with predominantly IFN-γ-secreting CD4 T cells and greater numbers of IgG2c than IgG1 antibody-secreting cells. The response to intramuscular vaccination with inactivated NC was similar in DR1 and B10 mice; the majority of CD4 T cells secreted IL-2 and most IgG antibody-secreting cells produced IgG2b or IgG2c. Our findings identify inherent host influences on characteristics of the virus-specific CD4 T cell and B cell responses that are restricted to the lung environment. Furthermore, we show that these host influences are substantially modulated by the type of infecting virus via the early induction of innate factors. Our findings emphasize the importance of immunization strategy for demonstrating inherent host differences in CD4 T cell and B cell responses.     

Memory B cells and CD8⁺ lymphocytes do not control seasonal influenza A virus replication after homologous re-challenge of rhesus macaques

This study sought to define the role of memory lymphocytes in the protection from homologous influenza A virus re-challenge in rhesus macaques. Depleting monoclonal antibodies (mAb) were administered to the animals prior to their second experimental inoculation with a human seasonal influenza A virus strain. Treatment with either anti-CD8α or anti-CD20 mAbs prior to re-challenge had minimal effect on influenza A virus replication. Thus, in non-human primates with pre-existing anti-influenza A antibodies, memory B cells and CD8α⁺ T cells do not contribute to the control of virus replication after re-challenge with a homologous strain of influenza A virus.     

Inhibition of T cell-mediated functions by MVM(i), a parvovirus closely related to minute virus of mice

A purified preparation of MVM(i), a murine parvovirus closely related to minute virus of mice (MVM), was found to inhibit various functions mediated by murine T cells in vitro. Addition of MVM(i) virus to secondary allogeneic mixed leukocyte cultures resulted in the inhibition of both lymphocyte proliferation (3H-thymidine incorporation) and the generation of cytolytic T lymphocyte activity but not interferon production. MVM(i) virus also inhibited the growth and cytolytic activity of several cloned, long-term Lyt-2+ cytolytic T cell lines. Furthermore, the antigen-induced proliferative responses of parasite- (Leishmania) specific Lyt-1+ T cells in vitro was abrogated by the addition of MVM(i) virus to the culture. Finally, the suppression of an in vitro antibody response to SRBC by MVM(i) virus was the result of the inhibition of T helper cells required for the B cell response. These suppressive effects were specific for MVM(i); parallel studies in which the prototype MVM parvovirus was used showed no significant inhibition in the various systems tested.     

TLR signaling fine-tunes anti-influenza B cell responses without regulating effector T cell responses

Influenza is a ssRNA virus that has been responsible for widespread morbidity and mortality; however, the innate immunological mechanisms that drive the adaptive anti-influenza immune response in vivo are yet to be fully elucidated. TLRs are pattern recognition receptors that bind evolutionarily conserved pathogen-associated molecular patterns, induce dendritic cell maturation, and consequently aid the development of effective immune responses. We have examined the role of TLRs in driving effective T and B cell responses against influenza virus. We found TLR3 and its associated adapter molecule, Toll/IL-R domain-containing adaptor-inducing IFN-beta, did not play a role in the development of CD4(+) or CD8(+) T cell responses against influenza virus, nor did they influence influenza-specific B cell responses. Surprisingly, TLR7 and MyD88 also played negligible roles in T cell activation and effector function upon infection with influenza virus; however, their signaling was critical for regulating anti-influenza B cell Ab isotype switching. The induction of appropriate anti-influenza humoral responses involved stimulation of TLRs on B cells directly and TLR-induced production of IFN-alpha, which acted to reduce IgG1 and increase IgG2a/c class switching. Notably, direct TLR signaling on B cells or T cell help through the CD40-CD40L interaction was sufficient to support B cell proliferation and IgG1 production, whereas IFN-alpha was critical for fine-tuning the nature of the isotype switch. Taken together, these data reveal that TLR signaling is not required for anti-influenza T cell responses, but through both direct and indirect means orchestrates appropriate anti-influenza B cell responses.     

A dominant idiotype in the antibody response against the influenza virus hemagglutinin. Serum and in situ analyses

PY206 is an Id associated with a BALB/c murine mAb described as being specific for the influenza A virus hemagglutinin. However, production of this Id by BALB/c mice immunized with influenza is low. This report shows that the PY206 Id is a dominant component of the anti-influenza antibody response in C57BL/6J strain mice infected intranasally with the influenza A/Hong Kong/168/(H3N2)[R] X-31 virus. High PY206 Id expression was linked to the IgHb Ig allotype locus. PY206 Id+ antibody-forming cells were identified in situ in cryostat sections of lymphoid tissues and idiotypic heterogeneity was identified among PY206+ B cells. Uninfected adult C57BL/6J mice had PY206 Id in their serum that lacked influenza binding specificity. In situ analysis of prenatal and neonatal spleen of uninfected C57BL/6J mice showed that the expansion of PY206 Id+ B cells occurred early in development. PY206+ cells were demonstrated in the lungs of influenza-infected mice but not in normal mice, establishing the capability to study this B cell population in the lung. This model offers the opportunity to manipulate the anti-influenza A virus hemagglutinin B cell response and to study the proliferation and migration of influenza-specific B cells in their native tissue environments.     

A synthetic decapeptide of influenza virus hemagglutinin elicits helper T cells with the same fine recognition specificities as occur in response to whole virus

The immunogenicity of an isolated murine helper T cell determinant was studied. Mice were immunized with a synthetic peptide corresponding to amino acid residues 111-120 of the influenza PR8 hemagglutinin (HA) heavy chain, a region previously identified as a major target of the helper T cell response to the HA molecule in virus-primed BALB/c mice. Lymph node T cells from these mice were fused with BW 5147 cells to produce T hybrids for clonal analysis of their recognition specificities. Three T cell hybridoma clones, obtained from two different mice, responded to the immunizing peptide when presented by syngeneic antigen-presenting cells. All of these clones responded also to antigen provided as intact wild-type PR8 virus. The fine specificity of the peptide-induced T cell hybridomas, in response to a panel of mutant and variant influenza viruses, was indistinguishable from the fine specificities of T cells to the corresponding region of the HA1 chain of the HA molecule which had been generated by priming of mice with intact wild-type virus. These results suggest that an immunogenic determinant is contained within the 111-120 sequence that is able to elicit anti-influenza virus T cells with a similar repertoire to those elicited by immunization with whole virus.     

Highly polymorphic products of both HLA-DR and HLA-DQ genes contribute to the polymorphism of the HLA-DR w13 haplotype

We studied the polymorphisms of HLA-DR and HLA-DQ products from HLA-DRw13 haplotypes by analyzing the restriction of influenza A-specific cloned T cells from an HLA-DRw13,DQw1,Dw19 homozygous individual. The results show that (1) some functional epitopes, which can be borne by either HLA-DR or HLA-DQ molecules, are strictly correlated with the HLA-Dw19 subtype of HLA-DRw13. This clearly indicates that both HLA-DR and HLA-DQ products contribute to the HLA-Dw19 subdivision of HLA-DRw13. (2) At least two different restricting epitopes are borne by DR products: one is correlated with the HLA-DRwl3 serologically defined specificity, which includes Dw19 and Dw18 haplotypes; the other is correlated with the only HLA-Dw19 subtype of HLA-DRwl3. (3) Restricting epitopes borne by DQ molecules have been found on Dw19 cells only. (4) DQ-restricted clones were unable to react with DQwl APC of any other haplotypes tested, including DR1, DR2-long, DR2-short, and DRw14, demonstrating a high degree of functional polymorphism among the serologically defined DQw1 specificities.Abbreviations used in this paper: APC antigen-presenting cells - cpm count per minute - HAU hemagglutinin units - IL-2 interleukin 2 - MHC major histocompatibility complex - mAb monoclonal antibody - PBM peripheral blood mononuclear cells - PHA phytohemagglutinin - pl isoelectric point - PMA phorbol myristic acetate - SD standard deviation     

A helper factor needed for the generation of mouse cytolytic T lymphocytes is made by tumor cell lines, cloned T cells, and spleen cells exposed to a variety of stimuli

A helper factor termed cytolytic T lymphocyte helper factor (CHF) that is needed for the generation of allospecific mouse cytolytic T lymphocytes (CTL) in vitro was produced by mouse spleen cells 3 to 4 days after the time when interleukin 2 (IL 2) had reached its maximal production. These kinetics were observed by stimulation of immune spleen cells with allogeneic tumor or spleen cells, with Sendai or influenza viral peptides, with virus infected cells, or with concanavalin A (Con A). CHF produced by rat spleen cells was able to help in the generation of mouse CTL, indicating that this cytokine was not restricted genetically. CHF could also be made by WEHI-3 and EL4 cell lines, as well as cloned cytolytic and helper T cells. The production of CHF by WEHI-3 cells argues that CHF is not IL 2. In addition, if CHF was not present early in the in vitro stimulation no CTL were generated, suggesting that CHF participated in the activation of CTL precursors. The addition of IL 2-containing conditioned medium to the CHF assay resulted in no substantial CTL generation, although significant cellular proliferation was observed. In contrast, CHF-containing conditioned medium allowed the generation of CTL in the absence of the same level of proliferation.     

Fine specificity of the in vitro antibody response to influenza virus by human blood lymphocytes

The fine specificity of anti-influenza antibody produced in vitro by human PBM stimulated with different strains of influenza virus was examined by competition binding in solid phase enzyme immunoassay. Most of the antibody produced in vitro is directed to strain-specific or cross-reactive determinants on the hemagglutinin molecule. The extent of cross-reactivity is dependent on the strain of virus used to stimulate PBM as well as the individual tested and presumably on his previous exposure to influenza viruses. PBM from some individuals produced antibody that bound to the stimulating strain of influenza virus but not to other strains of the same subtype. In other individuals, antibody was produced in vitro that cross-reacted with all viruses in the same subtype (e.g., H3N2; A/X31, A/X47, and A/Texas) but did not bind to other (H2N1 or H1N1) subtypes, and in a few individuals, extensive cross-reaction between subtypes was seen. The presence of antibody to hemagglutinin in these culture supernatants was confirmed by competition binding to highly purified hemagglutinin. This in vitro culture system allows the immunologic memory of individuals to a wide range of stimulating virus strains to be examined simultaneously in terms of specificity of the antibody response by human PBM to influenza virus after natural infection or immunization.