Development of cellular immunity to individual soluble antigens of Treponema pallidum during experimental syphilis

The contribution of individual specific molecules of Treponema pallidum subspecies pallidum to cellular immunity in experimental syphilis was evaluated by combining the techniques of Ag identification and purification with the lymphocyte proliferation assay. Proliferative responses of splenic lymphocytes from syphilitic rabbits to complex treponemal Ag and Con A were vigorous throughout the course of intratesticular infection (6, 10, 17, 30, and 210 days). Normal rabbits did not respond to any treponemal preparations and all rabbits failed to respond to normal rabbit testicular Ag (NRT). Seven defined treponemal Ag (47 kDa, 37 kDa, 35, 33-kDa, 30-kDa, 14 kDa, and 12 kDa) stimulated lymphocytes from infected rabbits. Cellular responses to the 37-kDa and 30-kDa fractions were evident by day 6 of infection and responses to the 35, 33-kDa and 14-kDa Ag were first detected on day 10; responsiveness to these Ag continued throughout the observation period. Cellular responses to the 47-kDa molecule were detectable but lower when compared with other individual Ag. Responsiveness to the 12-kDa Ag was not evident until 7 mo postinfection. Specific immunoblot reactivity of serum from rabbits used in this study generally correlated with the development of cellular reactivity to individual Ag of T. pallidum.     

Splenic macrophage function in early syphilitic infection is complex. Stimulation versus down-regulation

Macrophages are important regulatory cells that can both stimulate and down-regulate various immune functions. During syphilitic infection, these cells phagocytize, kill, and lyse Treponema pallidum. They also modulate early T cell activation by decreasing IL-2 production through secretion of PG. This report focuses on additional complexities of macrophage regulation. Non-adherent splenic cells were stimulated with Con A to induce IFN-gamma synthesis. High levels were detected in preparations from normal rabbits and much lower levels in preparations from infected rabbits. The organisms also readily stimulated IL-1 synthesis by adherent spleen preparations from normal but not from infected rabbits. When indomethacin was added to these latter preparations, this IL-1 defect was reversed, implicating PG in this down-regulation. Spleen cells were obtained from normal rabbits and from rabbits infected testicularly for 9 to 12 days. Infection elevated basal levels of class II Ia Ag on adherent cells. In addition, macrophage Ia expression was increased during 4 days of in vitro incubation with treponemes. Non-adherent spleen cells from infected animals inhibited two different macrophage functions. First, culture filtrates obtained after 48 h of incubation contained a soluble factor that subsequently decreased LPS-induced IL-1 synthesis. Second, when macrophages were co-incubated with non-adherent cells, treponemal stimulation of macrophage Ia expression was inhibited; this inhibition was reversed by indomethacin implicating prostaglandins in this down-regulation. In further experiments an exogenous source of IFN-gamma was incubated with adherent cells from infected rabbits. This stimulated macrophage function as shown by increased IL-1 synthesis and Ia expression and decreased PGE2 secretion. Results are discussed in terms of the complexities of immunoregulation by macrophages during syphilitic infection.     

Two subgroups of T helper cells in F1 hybrid mice revealed by negative selection to heterologous erythrocytes in vivo.

Generalized suppression of immunoglobulin G (IgG) synthesis detectable by depressed responses to heterologous antigens may be a mechanism by which certain parasites evade host defenses and establish chronic infections. To determine if such a mechanism occurs in syphilis, rabbits were infected with Treponema pallidum, and at weekly intervals thereafter these rabbits and uninfected controls were sensitized with SRBC. Seven days later the number of antibody-forming cells present in the spleen was determined by the Jerne plaque technique. After a transient suppression in the 1st week, IgM-PFC were elevated from up to 7 weeks after infection. The IgG response to SRBC was depressed early in infection and continued to decline to less than one-tenth of control levels over the next few weeks persisting throughout overt infection and returning to normal by the end of 2 months. IgG-PFC, and 2-ME-resistant hemagglutinins and hemolysins were also significantly depressed in infected rabbits after two immunizing doses of SRBC. These results suggest that the depressed IgG response caused by syphilitic infection may enable treponemes to evade host immunity by interfering with immunoregulatory mechanisms.     

Adoptive transfer of anti-syphilis immunity with lymphocytes from Treponema pallidum-infected guinea pigs

Spleen and lymph node cells taken from strain 2 and strain 13 guinea pigs at the peak of their primary immune response to cutaneous syphilitic infection could transfer partial protection to symptomatic disease to normal syngeneic recipients challenged with the Nichols strain of Treponema pallidum. These recipients of immune cells had significantly fewer treponemes disseminating to the regional lymph nodes and developed fewer and less severe cutaneous lesions that resolved faster than those in guinea pigs that had been infused with normal lymphoid cells. Immune donor cells also had the capacity to transfer specific delayed-type hypersensitivity responses for T. pallidum antigens. Both T and B cells were effective in conferring anti-syphilis immunity which was associated with the almost immediate development and persistence of substantially elevated levels of circulating anti-treponemal antibody in the protected recipients. Our findings in this adoptive transfer system provide the first direct experimental evidence implicating both cellular and humoral components of the immune response as important effector mechanisms in host resistance to the pathogenic spirochete causing venereal syphilis.     

Murine cutaneous leishmaniasis: resistance correlates with the capacity to generate interferon-gamma in response to Leishmania antigens in vitro

The kinetics of cell-mediated immunity developed during the course of Leishmania major infection in resistant (C57BL/6) and susceptible (BALB/c) mice were determined by using in vitro bioassays. Cells isolated from the lymph nodes draining the infected footpads were assayed for their proliferative responses to leishmania antigens (promastigote and amastigote) or to concanavalin A (Con A). Although lymph node cells (LNC) from both mouse strains proliferated to mitogen and antigen early after infection, both C57BL/6 and BALB/c mice developed diminished in vitro proliferative reactivity within 3 to 5 wk after infection. LNC from both mouse strains recovered lymphoproliferative reactivity to Con A (week 6), but only C57BL/6 mice regained reactivity to leishmania antigens. BALB/c cells remained unresponsive to leishmania antigens throughout the subsequent course of the infection. Supernatants derived from cultures of LNC that had been stimulated with Con A or leishmania antigens were assayed for interferon-gamma (IFN-gamma) by analyzing three distinct activities associated with IFN-gamma. Culture supernatants derived from leishmania antigen stimulation of LNC from infected C57BL/6 mice, but not BALB/c mice, were able to induce surface Ia on murine P388D1 cells. Ia-inducing activity was detectable in supernatants from C57BL/6 cells as early as 3 wk, and peaked by 5 wk after infection. Although cells from infected BALB/c mice never produced detectable IFN-gamma in response to leishmania antigens, LNC from both mouse strains produced readily detectable IFN-gamma in response to Con A throughout the course of infection. Culture supernatants that induced Ia on P388D1 cells were also capable of activating resident peritoneal macrophages to display leishmanicidal activity and of inhibiting encephalomyocarditis virus replication in murine fibroblasts. Each of these activities could be removed by prior incubation of the supernatants with rabbit heterologous anti-murine IFN-gamma sera or monoclonal rat-anti-murine IFN-gamma. The correlation of healer status with the capacity to generate IFN-gamma in vitro in response to leishmania antigens was examined in BALB/c mice that had been exposed to sublethal irradiation (550 rad) before infection. These animals have been previously shown to effectively resist L. major infection. Consistent with observations in the genetically resistant C57BL/6 mice, LNC from these animals demonstrated the capacity to respond to in vitro leishmania antigen stimulation with lymphoproliferation, and more importantly, by producing IFN-gamma.(ABSTRACT TRUNCATED AT 400 WORDS)     

Immunoregulation in experimental filariasis. I. In vitro suppression of mitogen-induced blastogenesis by adherent cells from Jirds chronically infected with Brugia pahangi

Nonspecific immunoregulatory events were examined in inbred jirds chronically infected with Brugia pahangi. The responsiveness of spleen cells from infected animals to the T cell mitogens PHA and Con A and to the B cell mitogens, LPS and PWM, was found to be suppressed by as much as 90% when compared with the reactivity of lymphocytes from normal animals. Furthermore, spleen cells from infected jirds were capable of suppressing the mitogen reactivity of normal spleen cells. Depletion of cells adherent to nylon wool, glass wool, or plastic alleviated the regulatory activity exerted by spleen cells from infected jirds. Addition of indomethacin, an inhibitor of prostaglandin synthetase, to cultures of spleen cells from infected animals did not alter the suppression observed. In contrast, lymphocytes from the peripheral lymph nodes of infected jirds did not exhibit depressed T cell mitogen reactivity and were incapable of suppressing the PHA or Con A responsiveness of normal lymph node cells. However, the reactivity of lymph node cells from infected jirds to B cell mitogens, LPS and PWM, was suppressed. These results imply the existence of multiple regulatory mechanisms, at least one of which is restricted to the spleen. The relevance of nonspecific regulation to development of parasite-specific immunologic reactivity and to the infection is discussed.     

Macrophage-mediated suppression of con A-induced IL-2 production in spleen cells from syphilitic rabbits

Blast transformation studies have indicated a diminished T cell response in spleen cell preparations from rabbits infected with Treponema pallidum. IL-2 synthesis by T lymphocytes is required for proliferation of these cells. Thus, Con A-induced IL-2 generation was measured in syphilitic animals infected for 9 to 14 days. IL-2 production in the infected rabbits was only one-half that observed for uninfected rabbits. This marked decrease in IL-2 was not caused by decreased IL-1 secretion by adherent cells from infected animals because similar levels were found in both infected and uninfected splenic cultures. This decrease was also not caused by an increase in infected spleen cell adsorption of IL-2; similar numbers of receptors for this IL were present in Con A-stimulated infected and uninfected splenic preparations. The inhibited IL-2 production in infected spleen cells was reversed upon removal of the adherent cells and also elevated upon addition of indomethacin to the cultures. PGE levels were also elevated in splenic cultures from infected animals. Finally, IL-2 synthesis, when evaluated at various days postinfection, showed that at 4 days, splenic cells generated twice as much IL-2 as uninfected cells. At 9 to 14 days, IL-2 levels were dramatically decreased (50% lower than that observed in uninfected cultures), and suppression of IL-2 by adherent cells was observed as late as 35 days post-infection. We propose that premature down regulation (suppression) of IL-2 secretion is mediated by adherent cells via a cyclo-oxygenase product, most likely PGE. These results may explain why most, but not all, treponemes are cleared during infection, and why the secondary manifestations of the disease occur.     

Autoantibodies to creatine kinase in rabbits infected with Treponema pallidum

Sera from rabbits infected intratesticularly with Treponema pallidum (Nichols) for 30 days were examined for autoantibody reactivity against muscle and testis extracts by Western immunoblotting. Syphilitic sera (30 day) reacted with an autoantigen of 43,000 daltons in muscle extracts. The antigen was shown to be creatine kinase (CK). Studies with the use of an anti-CK ELISA showed that the autoantibody to CK first appeared 3 wk after infection, declined by 7 wk infection, and was absent in rabbits "mock"-infected with heat-killed T. pallidum. CK activity was not detected in sonicated or intact, washed T. pallidum, suggesting that the antibody was not produced in response to treponemal CK.     

Trypanosoma cruzi: maintenance of parasite-specific T cell responses in lymph nodes during the acute phase of the infection

Mice infected with 5 x 10(3) forms of Trypanosoma cruzi showed a transient, but severe impairment of in vitro spleen cell responses to parasite antigens and to Concanavalin A (Con A). In contrast, inguinal and periaortic lymph node (LN) cells displayed high parasite-specific proliferative responses and only a partial reduction of the Con A-induced proliferation during the acute and chronic phases of infection. Lymphocytes that underwent blastic transformation in T. cruzi-stimulated cell cultures were of the L3T4+ phenotype. Suppression of spleen cell responses occurred in the acute phase whether mice were infected with high (3 x 10(5] or low (5 x 10(3] doses of T. cruzi by intraperitoneal or subcutaneous route. Suppression of the T. cruzi-specific proliferative response of LN cells was only observed in mice infected with high subcutaneous inocula. This suppression, however, was restricted to the LNs draining the site of inoculation without affecting distant LNs. Supernatants from parasite-stimulated proliferating LN cells displayed low or undetectable T cell growth factor (TCGF) activity, in contrast with the high TCGF levels found in supernatants of the same cells stimulated with Con A. Low levels of TCGF were also detected in cultures of LN cells from mice immunized with T. cruzi extracts. Neither the T. cruzi antigen used for in vitro stimulation nor the LN cell supernatants from infected mice inhibited TCGF activity. These findings indicate that (1) parasite-specific responses are present in the LN compartment throughout the acute phase of T. cruzi infection in mice and (2) the proliferative response of L3T4+ LN cells from infected mice to T. cruzi antigens is not associated with a high TCGF secretory response.     

Herpes simplex virus type 1-specific cytotoxic T lymphocytes recognize virus nonstructural proteins.

The specificity of herpes simplex virus type 1-specific cytotoxic T cells was examined with target cells expressing either input viral structural antigens or antigens resulting from permissive infection or cells from an interrupted infection in which they expressed predominantly nonstructural immediate-early proteins. These studies indicated that only an insignificant minority of cytotoxic T cells recognized the input viral antigens, whereas a significant proportion (20 to 35%) recognized target cells that expressed the immediate-early proteins despite the absence of serologically detectable viral antigens upon the infected cell surface. The finding that a significant proportion of cytotoxic T-cell populations obtained from the draining lymph nodes of mice acutely infected with herpes simplex virus type 1 also recognized immediately-early gene-expressing target cells indicates the importance of nonstructural herpes simplex virus proteins to antiviral immunity in vivo.     

Comparison of local and systemic responsiveness of lymphocytes in vitro to Bovicola ovis antigen and Concanavalin A in B. ovis-infested and naive lambs

The in vitro proliferation assay was used to determine lymphocyte responsiveness to soluble antigen of B. ovis and to Concanavalin A (Con A) in peripheral blood, spleen and various lymph nodes from B. ovis-infested and naive lambs. From March to July, an assay of monthly blood samples showed generally higher proliferative responses to antigen and Con A in B. ovis-infested than naive lambs. The proliferative response of cells from the skin-draining prescapular lymph nodes to B. ovis antigen was significantly higher in B. ovis-infested than naive lambs. Responses of cells from the medial iliac, mediastinal and mesenteric lymph nodes (which do not receive lymph from the skin) and spleen showed no significant differences between groups. Within the B. ovis-infested lambs, the response of cells from the prescapular lymph node was significantly higher than that from any other lymphoid organ examined. Responsiveness of the prescapular, medial iliac and mesenteric lymph node and spleen cells to Con A was not significantly different between groups, while mediastinal lymph node cells showed a significantly higher response in B. ovis-infested lambs. The data indicate that the antigen-specific cellular immune response is operating mainly locally, at the level of the skin and draining lymph nodes. Responses to the T cell mitogen Con A did not support non-specific immunodepression as reported in other ectoparasite/host systems.     

Lymphocyte function in experimental African trypanosomiasis. VIII. Loss of suppressor T cell function in lymph nodes

The immunosuppression that occurs in mice experimentally infected with African trypanosomiasis has been examined further. In the present study we have examined lymph node cells from Trypanosoma rhodesiense-infected C57Bl/6J mice for the ability to produce mitogen induced antigen-nonspecific suppressor T cells (Ts). Inguinal, mesenteric, and brachial lymph node cells were harvested from uninfected control mice and from mice at different periods of infection. These cells were cultured with or without concanavalin A (Con A) for 48 hr to induce Ts activity. After stimulation, the control and infected lymph node cells were passed over Sephadex G-10 columns to remove suppressor macrophages that arise during the infection from Con A-induced Ts. The column passed cells were then added to normal mouse responder spleen cells in a primary in vitro antibody response culture system with sheep erythrocytes (SRBC) as antigen. The resultant plaque-forming cell responses to SRBC indicated that Ts function was not induced in infected lymph node cell populations. However, early in the infection, a stimulatory signal was provided by both the untreated and Con A-treated infected lymph node cells, which was lost in the terminal stage. Determinations of T cell subpopulations revealed that the infected Lyt 2.2-bearing subpopulation was not significantly altered from normal controls. We conclude that T. rhodesense infected mice fail to mount normal lymph node cell antigen nonspecific Ts responses and that this loss of activity may be due to an intrinsic dysfunction in the suppressor T cell population.     

Assessment of cell-surface exposure and vaccinogenic potentials of Treponema pallidum candidate outer membrane proteins

Syphilis, a sexually transmitted infection caused by the spirochetal bacterium Treponema pallidum, remains a global public health problem. T. pallidum is believed to be an extracellular pathogen and, as such, the identification of T. pallidum outer membrane proteins that could serve as targets for opsonic or bactericidal antibodies has remained a high research priority for vaccine development. However, the identification of T. pallidum outer membrane proteins has remained highly elusive. Recent studies and bioinformatics have implicated four treponemal proteins as potential outer membrane proteins (TP0155, TP0326, TP0483 and TP0956). Indirect immunofluorescence assays performed on treponemes encapsulated within agarose gel microdroplets failed to provide evidence that any of these four molecules were surface-exposed in T. pallidum. Second, recombinant fusion proteins corresponding to all four candidate outer membrane proteins were used separately, or in combination, to vaccinate New Zealand White rabbits. Despite achieving high titers (>1:50,000) of serum antibodies, none of the rabbits displayed chancre immunity after intradermal challenge with viable T. pallidum.     

Lymphoid cell kinetics in guinea pigs infected with Trichostrongylus colubriformis: tritiated thymidine uptake in gut and allied lymphoid tissue, humoral IgE and hemagglutinating antibody responses, delayed hypersensitivity reactions, and in vitro lymphocyte transformations during primary infections

The kinetics of the lymphocyte responses of Trichostrongylus colubriformis-infected and normal guinea pigs were measured by the in vivo uptake of tritiated thymidine either as dpm ³H/mg tissue or as the percentage change in [³H] -labeled lymphoblasts in autoradiographs of tissue impression smears and sections. The lymphoid response was predominantly a local one centering on the infected area of the small intestine. The greatest lymphocyte reactions as assessed by counts of labeled lymphoblasts occurred in the Peyer's patches and mesenteric lymph nodes where the peak responses took place 11 and 6 days after infection, respectively. The local nature of the responses was exemplified by the fact that the mesenteric lymph nodes of the anterior small intestine showed a peak response on the sixth day but the response from the posterior small intestine peaked 7 days later. A similar but less dramatic relationship existed among the Peyer's patches. In addition no labeled lymphoblast response was elicited in the inguinal lymph nodes or cecal lymphoid patches throughout the infection and the first increased responsiveness of the spleen did not take place until after Day 13, by which time the lymphoid proliferations associated with the infected intestine had subsided. Initially, the spleen showed a marked depletion of labeled blast cells during the first 7 days of the infection. This was taken as indicating at the time the infection was being established the export of cells capable of transformation in response to parasite antigen. This was supported by the observation that large numbers of phytohemagglutinin responsive lymphocytes were found in the peripheral circulation at this time. The in vitro responsiveness of peripheral lymphocytes to T. colubriformis antigen was also studied. Positive lymphocyte transformations first occurred 6 days after infection but thereafter declined to the normal level by Day 13; the peak transformation ratio was found 25 days after infection but by Day 38 it had declined to a low but persistently positive level. There was a correlation between the circulation of specifically sensitized cells, probably of thymic origin, IgE antibody titers, and the development of positive dermal delayed hypersensitivity reactions in infected guinea pigs, suggesting a close relationship among these three immunological phenomena.All lymphoblast responses in Peyer's patches, mesenteric lymph nodes, and lamina propria of the intestine were completed before the immune elimination of the parasite commenced 10 days after infection. During the first 10 days of infection specifically sensitized lymphocytes appeared and disappeared from the circulation. The loss of circulating sensitized lymphocytes at the time immune elimination of the parasite was taking place in the gut suggested that the sensitized cells were “homing-in” on the local area of infection. After the immune elimination of the parasite had commenced, the level of sensitized lymphocytes and IgE antibodies then increased rapidly in the blood. Evidence from the kinetics of the hemagglutinating antibodies indicated that stage specific antigens occur in T. colubriformis.     

Polypeptides of Treponema pallidum: progress toward understanding their structural, functional, and immunologic roles. Treponema Pallidum Polypeptide Research Group.

Treponema pallidum subsp. pallidum, the spirochete that causes syphilis, is unusual in a number of respects, including its small genome size, inability to grow under standard in vitro culture conditions, microaerophilism, apparent paucity of outer membrane proteins, structurally complex periplasmic flagella, and ability to evade the host immune responses and cause disease over a period of years to decades. Many of these attributes are related ultimately to its protein content. Our knowledge of the activities, structure, and immunogenicity of its proteins has been expanded by the application of recombinant DNA, hybridoma, and structural fractionation techniques. The purpose of this monograph is to summarize and correlate this new information by using two-dimensional gel electrophoresis, monoclonal antibody reactivity, sequence data, and other properties as the bases of polypeptide identification. The protein profiles of the T. pallidum subspecies causing syphilis, yaws, and endemic syphilis are virtually indistinguishable but differ considerably from those of other treponemal species. Among the most abundant polypeptides are a group of lipoproteins of unknown function that appear to be important in the immune response during syphilitic infection. The periplasmic flagella of T. pallidum and other spirochetes are unique with regard to their protein content and ultrastructure, as well as their periplasmic location. They are composed of three core proteins (homologous to the other members of the eubacterial flagellin family) and a single, unrelated sheath protein; the functional significance of this arrangement is not understood at present. Although the bacterium contains the chaperonins GroEL and DnaK, these proteins are not under the control of the heat shock regulon as they are in most organisms. Studies of the immunogenicity of T. pallidum proteins indicate that many may be useful for immunodiagnosis and immunoprotection. Future goals in T. pallidum polypeptide research include continued elucidation of their structural locations and functional activities, identification and characterization of the low-abundance outer membrane proteins, further study of the immunoprotective and immunodiagnostic potential of T. pallidum proteins, and clarification of the roles of treponemal proteins in pathogenesis.     

Circulating immune complexes in experimental syphilis and their relation to immunological response against Treponema pallidum

It was found that circulating immune complexes (CIC) were formed in rabbits at different times after infection with Treponema pallidum. The CIC which appeared at the beginning of the disease were short-lived (2-6 weeks) but those appearing later than 20 weeks after infection remained for 10-25 weeks. CIC contained both IgM and IgG classes of immunoglobulin. The antibodies present in CIC were found to be specific and nonspecific for T. pallidum. The presence of CIC led to a marked decline of treponemal antibodies in rabbit sera. The cell-mediated immune response measured by the macrophage migration inhibition (MMI) test at the beginning of the disease (up to 12 weeks) was not decreased. However, when syphilis lasted for more than 14 weeks and when CIC were formed mainly from IgG, a distinct decrease in the ability of lymphocytes to cause MMI was observed. These findings strongly suggest that IgG-complexes suppress the immunological responsiveness of lymphocytes against T. pallidum which in turn facilitates the multiplication of treponemes in the host.     

The ability of peripheral blood mononuclear cells of rabbits infected with Treponema pallidum to produce IL-2

Abstract It was previously found that the cell-mediated immune response involved in protection against Treponema pallidum is distinctly suppressed during some periods in the course of syphilis infection in rabbits. This may be a result of the weak ability of cells to produce Interleukin-2 (IL-2) as well as of IL-2 absorption. The ability of peripheral blood mononuclear cells (PBMC) of syphilitic rabbits to produce IL-2 develops within the first two weeks after infection reaching a maximum in about the eleventh week. In infection of longer duration, this capability was distinctly lowered. This low level of activity (no higher than in PBMC of normal rabbits) was maintained for 31 weeks. The ability of PBMC to absorb IL-2, in parallel with its production, was found at the same time in the course of syphilis infection (7–11 weeks). In long-lasting syphilis (more than 12 weeks) both abilities seem to be inhibited. Sera of syphilitic rabbits were found to have a higher level of IL-2 inhibitor than those of normal rabbits. Only in syphilis lasting 9 to 11 weeks, when the production of IL-2 was the greatest, was the level of IL-2 inhibitor nearly the same as in normal rabbit sera. In syphilis lasting longer, the increased level of inhibitor was accompanied by a decreased ability of cells to produce IL-2. These findings suggest that IL-2 inhibitor may be bound to IL-2 or IL-2 receptor on T lymphocytes and in this way would lead to weakening of T cell function and resistance against Treponema pallidum infection.     

Suppression of immune response by lung cells in experimental tuberculosis

In vitro proliferative response of lung cells from mice infected with Mycobacterium tuberculosis H37Rv against PPD and Con A was studied. It was shown that the infected lung contained immune T cells, but their response in vitro was totally inhibited by plastic and nylon wool adherent suppressor cells. The whole population of lung cells from infected, but not intact mice, efficiently suppressed the proliferative response of immune lymph node cells against various antigens (non-specific suppression). The inhibition of response again depended on the presence of plastic adherent lung cells. Our data suggest that at least two suppressor pathways are induced in the course of tuberculosis infection: one being specific for mycobacterial antigens and other non-specific. Both types of suppressor pathways depend on the plastic adherent lung cells from tuberculosis lesion.     

Further evidence for hyaluronidase activity of Treponema pallidum

The presence of hyaluronidase in preparations of Treponema pallidum was previously shown using acidified bovine serum albumin reactions and Ouchterlony immunodiffusion. To expand on these preliminary findings more sensitive techniques of viscometry, additional immunologic reactions, and altered capillary permeability were used to characterize treponemal-associated hyaluronidase. The pathogens T. pallidum and T. pertenue degraded hyaluronic acid, whereas the nonpathogens T. denticola and T. vincentii did not. As syphilitic infection progressed, hyaluronidase activity decreased; organisms harvested from 14-day testicular infections degraded hyaluronic acid less rapidly than organisms from 4-day infections. Uninfected rabbit testicular extract also exhibited significant enzyme activity. The neutralizing activity of immune sera was decreased by prior adsorption with bovine hyaluronidase, suggesting that some of the neutralizing factors are associated with this enzyme. Radioimmunoassay was used to quantitate antibodies to hyaluronidase in immune sera. Antihyaluronidase sera were isolated from rabbits immunized with bovine hyaluronidase. Treponema pallidum, as well as uninfected rabbit testicular extract, cross-reacted with these antisera. Immunofluorescence indicated that the hyaluronidase was uniformly distributed along the treponemal surface. As a final indicator of hyaluronidase activity, alterations in capillary permeability were detected 1 h after intradermal injection of T. pallidum.     

Activation, differentiation, and migration of naive virus-specific CD8+ T cells during pulmonary influenza virus infection

The low precursor frequency of individual virus-specific CD8(+) T cells in a naive host makes the early events of CD8(+) T cell activation, proliferation, and differentiation in response to viral infection a challenge to identify. We have therefore examined the response of naive CD8(+) T cells to pulmonary influenza virus infection with a murine adoptive transfer model using hemagglutinin-specific TCR transgenic CD8(+) T cells. Initial activation of CD8(+) T cells occurs during the first 3 days postinfection exclusively within the draining lymph nodes. Acquisition of CTL effector functions, including effector cytokine and granule-associated protease expression, occurs in the draining lymph nodes and differentially correlates with cell division. Division of activated CD8(+) T cells within the draining lymph nodes occurs in an asynchronous manner between days 3 and 4 postinfection. Despite the presence of Ag for several days within the draining lymph nodes, dividing T cells do not appear to maintain contact with residual Ag. After multiple cell divisions, CD8(+) T cells exit the draining lymph nodes and migrate to the infected lung. Activated CD8(+) T cells also disseminate throughout lymphoid tissue including the spleen and distal lymph nodes following their emigration from draining lymph nodes. These results demonstrate an important role for draining lymph nodes in orchestrating T cell responses during a local infection of a discrete organ to generate effector CD8(+) T cells capable of responding to infection and seeding peripheral lymphoid tissues.