Plasmacytoid dendritic cells do not migrate in intestinal or hepatic lymph

Plasmacytoid dendritic cells (pDCs) recognize pathogen-associated molecules, particularly viral, and represent an important mechanism in innate defense. They may however, also have roles in steady-state tolerogenic responses at mucosal sites. pDCs can be isolated from blood, mucosa, and lymph nodes (LNs). Although pDCs can express peripherally derived Ags in LNs and at mucosal sites, it is not clear whether pDCs actually migrate from the periphery in lymph or whether LN pDCs acquire Ags by other mechanisms. To determine whether pDCs migrate in lymph, intestine or liver-draining LNs were removed and thoracic duct leukocytes (TDLs) were collected. TDLs expressing MHC-II and CD45R, but not TCRalphabeta or CD45RA, were then analyzed. These enriched TDLs neither transcribe type I IFNs nor secrete inflammatory cytokines in response to viral stimuli in vitro or after a TLR7/8 stimulus in vivo. In addition, these TDLs do not express CD5, CD90, CD200, or Siglec-H, but do express Ig, and therefore represent B cells, despite their lack of CD45RA expression. Intestinal and hepatic lymph are hence devoid of bona fide pDCs under both steady-state conditions and after TLR7/8 stimulation. This shows that any role for pDCs in Ag-specific T cell activation or tolerance must differ from the roles of classical dendritic cells, because it cannot result from peripheral Ag capture, followed by migration of pDCs via lymph to the LN.

Recruitment and proliferation of CD4+ T cells in synovium following adoptive transfer of adjuvant-induced arthritis

Adjuvant-induced arthritis can be transferred to naive Dark Agouti (DA) strain (DA.CD45.1) rats by thoracic duct (TD) lymphocytes. Disease can be re-induced in convalescent rats by further transfer of arthritogenic cells, suggesting that resolution of the adoptive disease is not due to active regulation. To examine whether resolution is due to exhaustion of effector cells, we transferred the disease to DA.CD45.1 recipients, using CD4+ T cells from DA.CD45.2 donors. At the height of the adoptively transferred disease, donor cells comprised only 5-10% of recirculating CD4+ T cells but they accounted for approximately 40% of the CD4+ T cells in synovium-rich tissues of the hind paws. Approximately 65% of the donor cells in the synovium expressed a marker of proliferation (Ki-67 antigen). Division of CD4+ T cells continued in shielded paws after suppression of the recirculating pool of lymphocytes by selective irradiation. Intravenously injected CD4+ TD T lymphoblasts from arthritic donors were recruited to normal paws and, in greater numbers, to paws of animals with existing arthritis. Survival of the [125I]iodo-deoxyuridine-labeled lymphoblasts was greater in animals with existing arthritis. We conclude that effector CD4+ T cells in target tissues can proliferate in response to autoantigens and exhibit enhanced survival. However, without a continuous supply, adoptively transferred effector cells do not produce autonomous local disease, due to limits to their lifespan and ability to replicate indefinitely.

Phenotype and function of rat dendritic cell subsets

Dendritic cells (DC) comprise phenotypically-distinct subsets that sub-serve distinct functions in immune induction. Understanding the biology of DC subsets in vivo is crucial for the understanding of immune regulation and its perturbations in disease. This review focuses on the phenotype and functions of rat DC subsets and compares these with subsets identified in other species. Our research has concentrated on DC migrating in lymph. DC migrate constitutively from peripheral tissues to draining nodes, probably to induce/maintain tolerance to self- or harmless foreign antigens. After removal of mesenteric lymph nodes (MLN) in the rat, healing of afferent and efferent lymphatics permits migrating intestinal DC (iLDC) to be collected from the thoracic duct. We have shown that iLDC consist of least two subsets that differ in phenotype, in situ distribution and function. CD4+/SIRPalpha+ iLDC are highly immunostimulatory, but are excluded from T cell areas of MLN. In contrast, CD4-/SIRPalpha- iLDC are less potent stimulators of T cells, but carry material from apoptotic enterocytes to T cell areas of MLN. Similar subsets exist in both lymph nodes and spleen. It has been shown that phenotypically-similar subsets migrate in skin-draining lymph in cattle and sheep. We and others have shown that splenic CD4-/SIRPalpha- DC can phagocytose allogeneic cells in vitro, are poor stimulators of CD8+ T cells, and can lyse NK-sensitive target cells. Although some of our data suggest that rat CD4-/SIRPalpha- DC may equate to murine CD8+ DC, there is at present insufficient evidence to be confident of this.

Temporal changes in the distribution of thoracic duct lymphoblasts to synovium and other tissues of rats with adjuvant-induced arthritis

The distribution of lymphoblasts(lymphocytes in cell cycle) obtained from the central lymph of donor rats and transferred adoptively to syngeneic recipients has been shown previously to be influenced by the presence of arthritis in either donor or recipient rats. The intent of the present study was to examine patterns of distribution of lymphoblasts in the early period after transfer, when extravasation of donor lymphoblasts was expected to occur. Thoracic duct lymphoblasts labelled in vitro with [125I]-iododeoxyuridine were detected in recipient rats by external radiometry and autoradiography. Irrespective of donor status, fewer donor lymphoblasts accumulated in the feet of normal recipients when compared to arthritic recipients at 15 min, 2 h and 24 h after cell transfer.When recipients of similar disease status were compared, the percentages of injected lymphoblasts from normal and arthritic donors recovered in the feet were similar at 15 min and 2 h after transfer. The proportions of lymphoblasts recovered in the feetat 24 h after injection declined in normal recipients and arthritic recipients of cells from normal donor rats. Importantly,this decline did not occur when both the donor and the recipient were arthritic. In the hindpaws, donor lymphoblasts were located predominantly in the bone marrow, except in transfers between arthriticrats, when at 24 h they were predominantly in the synovium. At 15 min, lymphoblasts were detected within the lumen of vessels within synovium, whereas by 2 h extravasation of these cells was evident. In conclusion, lymphoblasts accumulate more readily in hindfeet that are inflamed. In the early hours after injection, lymphoblasts from normal and arthritic donors are recruited equally, but these early levels are only maintained for 24 hin the combination of arthritic donor and arthritic recipient. Adramatic change in the proportion of lymphoblasts located in synoviumat this later time suggests that a dynamic process of relocation,retention and/or local cell division maintains the numbers of arthritic donor cells in the latter combination.

Characterization of thoracic duct cells that transfer polyarthritis

Polyarthritis may result from the haematogenous distribution of arthritogenic effector lymphocytes that emerge in the efferent lymph and pass through the thoracic duct (TD) to the circulation. We therefore examined whether TD cells collected from rats in the late prodrome of adjuvant-induced arthritis (AA) could transfer polyarthritis adoptively and whether these cells included a subpopulation of arthritogenic cells that could be identified phenotypically. Unfractionated TD cells collected from donor rats 9 days after adjuvant inoculation were injected intravenously into normal syngeneic recipients in numbers equivalent to the overnight harvest from a single donor. TD cell subpopulations, equivalent in number to proportions in the same inoculum, were prepared by negative selection. Unfractionated TD cells transferred polyarthritis without in vitro stimulation or conditioning of recipient animals. Abrogation of arthritogenicity by depletion of alpha/beta TCR(+) cells showed that the polyarthritis was transferred by T cells. Negatively selected CD4(+) but not CD8(+) TD cells transferred AA. An arthritogenic subpopulation of CD4(+) T cells, enriched by either negative or positive selection, expressed the activation markers CD25 (IL-2 receptor alpha), CD71 (transferrin receptor), CD134 (OX40 antigen) and MHC class II. Cells expressing these markers were more numerous in TD lymph from arthritic rats than in lymph from normal rats and they included the majority of large CD4(+) T cells. Thus, arthritogenic effector T cells bearing activation markers are released into the central efferent lymph in the late prodrome of AA. Recruitment of these arthritogenic cells to synovium probably determines the polyarticular pattern of AA.

Phospholipase A(2)--derived neutral lipids from posthemorrhagic shock mesenteric lymph prime the neutrophil oxidative burst

BACKGROUND

Our previous work identified posthemorrhagic shock mesenteric lymph (PHSML) lipids as key elements in polymorphonuclear neutrophil (PMN)--provoked acute lung injury. We hypothesize that gut phospholipase A(2) (PLA(2)) is responsible for the generation of proinflammatory lipids in PHSML that primes circulating PMNs for enhanced oxidative burst.

METHODS

Mesenteric lymph was collected from rats (n = 5) before (preshock), during the induction of hemorrhagic shock (mean arterial pressure, 40 mm Hg x 30 minutes), and at resuscitation (shed blood + 2x lactated Ringer's solution). PLA(2) inhibition (quinacrine, 10 mg/kg, intravenously) was given before shock was induced. Extracted lipids were separated by normal phase high-pressure liquid chromatography and resuspended in albumin. PMNs were exposed to a 5% vol:vol concentration of eluted lipids and activated with N-formyl-methionyl-leucyl-phenylalanine (1 micromol/L). Superoxide production was assessed by cytochrome C reduction.

RESULTS

High-pressure liquid chromatography--extracted neutral lipids of lymph collected before hemorrhagic shock did not prime the PMN oxidase, whereas isolated neutral lipids of postshock lymph primed PMNs 2.6- +/- 0.32-fold above baseline (P <.05). PLA(2) inhibition returned PHSML neutral lipid priming to baseline levels.

CONCLUSIONS

PLA(2) inhibition before hemorrhagic shock abrogates the neutrophil priming effects of PHSML through reduction of the accumulation of proinflammatory neutral lipids. Identification of these PLA(2)-dependent lipids provides a mechanistic link that may have therapeutic implications for postshock acute lung injury.

Recent thymic emigrants (CD4+) continuously migrate through lymphoid organs: within the tissue they alter surface molecule expression

T-cell progenitors migrate from bone marrow (BM) into the thymus. After maturation they are released as recent thymic emigrants (RTE) into the periphery ensuring the diversification of the T-cell repertoire. Both the kinetics with which RTE migrate through the periphery and the surface molecules they express are still unclear. In 1- and 18-month-old Lewis rats CD4+ RTE were identified in blood, spleen, lymph node, and thoracic duct lymph by flow cytometry (CD45RC- and CD90+), were differentiated from CD4+ naive (CD45RC+) and memory T cells (CD45RC-CD90-), and were characterized regarding the expression of surface molecules. Both in 1- and 18-month-old animals the percentage of RTE among the CD4+ population in blood was comparable to that in all other compartments. Surprisingly, RTE expressed alpha4-integrin, LFA-1, and interleukin (IL)-2 receptor at a significantly higher level than naive T cells and more comparable to memory T cells. Within lymphoid tissues RTE, naive, and memory T cells significantly upregulated the expression of CD44 and ICAM-1, and downregulated the expression of L-selectin. These changes were reversed before the cells re-entered the blood. Thus, our data indicate that CD4+ RTE travel through the periphery of young and old rats like mature T cells, continuously modulating their surface molecule expression.

B cell-deficient (mu MT) mice have alterations in the cytokine microenvironment of the gut-associated lymphoid tissue (GALT) and a defect in the low dose mechanism of oral tolerance

Peripheral immune tolerance following i.v. administration of Ag has been shown to occur in the absence of B cells. Because different mechanisms have been identified for i.v. vs low dose oral tolerance and B cells are a predominant component of the gut-associated lymphoid tissue (GALT) they may play a role in tolerance induction following oral Ag. To examine the role of B cells in oral tolerance we fed low doses of OVA or myelin oligodendrocyte glycoprotein to B cell-deficient ( microMT) and wild-type C57BL/6 mice. Results showed that the GALT of naive wild-type and microMT mice was characterized by major differences in the cytokine microenvironment. Feeding low doses of 0.5 mg OVA or 250 microg myelin oligodendrocyte glycoprotein resulted in up-regulation of IL-4, IL-10, and TGF-beta in the GALT of wild-type but not microMT mice. Upon stimulation of popliteal node cells, in vitro induction of regulatory cytokines TGF-beta and IL-10 was observed in wild-type but not microMT mice. Greater protection against experimental autoimmune encephalomyelitis was found in wild-type mice. Oral tolerance in microMT and wild-type mice was found to proceed by different mechanisms. Anergy was observed from 0.5 mg to 250 ng in microMT mice but not in wild-type mice. Increased Ag was detected in the lymph of microMT mice. No cytokine-mediated suppression was found following lower doses from 100 ng to 500 pg in either group. These results demonstrate the importance of the B cell for the induction of cytokine-mediated suppression associated with low doses of Ag.

CD25 is a marker for CD4+ thymocytes that prevent autoimmune diabetes in rats, but peripheral T cells with this function are found in both CD25+ and CD25- subpopulations

Previously we have shown that autoimmune diabetes, induced in rats by a protocol of adult thymectomy and split-dose gamma irradiation, can be prevented by the transfer of a subset of CD4+ T cells with a memory phenotype (CD45RC-), as well as by CD4+CD8- thymocytes, from syngeneic donors. Further studies now reveal that in the thymus the regulatory cells are observed in the CD25+ subset of CD4+CD8- cells, whereas transfer of the corresponding CD25- thymocyte subset leads to acceleration of disease onset in prediabetic recipients. However, in the periphery, not all regulatory T cells were found to be CD25+. In thoracic duct lymph, cells that could prevent diabetes were found in both CD25- and CD25+ subsets of CD4+CD45RC- cells. Further, CD25- regulatory T cells were also present within the CD4+CD45RC- cell subset from spleen and lymph nodes, but were effective in preventing diabetes only after the removal of CD25- recent thymic emigrants. Phenotypic analysis of human thymocytes showed the presence of CD25+ cells in the same proportions as in rat thymus. The possible developmental relationship between CD25+ and CD25- regulatory T cells is discussed.

Identical T cell clones are located within the mouse gut epithelium and lamina propia and circulate in the thoracic duct lymph

Murine gut intraepithelial (IEL) T cell receptor (TCR)-alpha/beta lymphocytes bearing CD8alpha/13 or CD8alpha/alpha coreceptors have been shown previously to express different oligoclonal TCR beta chain repertoires in the same mouse, in agreement with other evidence indicating that these two populations belong to different ontogenic lineages, with only CD8alpha/beta+ IELs being fully thymus dependent. CD8alpha/beta+, but not CD8alpha/alpha+, T lymphocytes are also present in the lamina propria. Here, we show that CD8alpha/beta+ lymphocytes from the lamina propria and the epithelium are both oligoclonal, and that they share the same TCR-beta clonotypes in the same mouse, as is also the case for CD4alpha T cells. Furthermore, identical T cell clones were detected among CD8alpha/beta IELs and CD8alpha/beta+ blasts circulating into the thoracic duct (TD) lymph of the same mouse, whereas TD small lymphocytes are polyclonal. These findings must be considered in light of previous observations showing that T blasts, but not small T lymphocytes, circulating in the TD lymph have the capacity of homing into the gut epithelium and lamina propria. These combined observations have interesting implications for our understanding of the recirculation of gut thymus-dependent lymphocytes and their precursors, and of the events leading up to the selection of their restricted TCR repertoire.

Lymphocyte trafficking: CD4 T cells with a 'memory' phenotype (CD45RC-) freely cross lymph node high endothelial venules in vivo

Antigen encounter not only induces a change in surface expression of CD45RC isoforms in the rat from a high (CD45RC+) to a low molecular weight molecule (CD45RC-), but also stimulates changes in expression of adhesion molecules that regulate CD4 T-cell migration. T cells with an activated or 'memory' phenotype (CD45RC-) are thought to enter lymph nodes almost exclusively via afferent lymphatics whereas T cells in a resting state (CD45RC+) migrate across high endothelial venules (HEV). The present study monitored the rapid recirculation from blood to lymph of allotype-marked CD45RC T-cell subsets. Surprisingly, we found that CD45RC- CD4 T cells entered the thoracic duct slightly faster and reached peak numbers 3 hr earlier (18 hr) than did the CD45RC+ subset. To determine whether the entrance of CD45RC+ and RC- subsets was restricted to HEV and afferent lymphatics, respectively, recirculation of CD4 T cells was monitored in mesenteric lymphadenectomized (MLNx) rats (on healing the intestinal afferent lymphatics are joined directly to the thoracic duct), or in recipients that had had the mesenteric lymph node (MLN) acutely (2-3 hr) deafferentized (entry would be restricted to HEV). In these studies CD45RC- CD4 T cells entered the MLN across HEV on an equal basis with T cells expressing a CD45RC+ phenotype. Contrary to currently held dogma the results showed that, in vivo, CD4 T cells with a memory phenotype freely enter lymph nodes (LN) across HEV as well as via afferent lymphatics.

Phenotypical characterization of cells in the thoracic duct of patients with and without systemic inflammatory response syndrome and multiple organ failure

The subset composition and recirculation properties of the migrating lymphocyte pool in humans is largely unknown. The present study was conducted in order to phenotypically characterize cells in human thoracic duct lymph of patients under non-inflammatory and inflammatory conditions. These data were compared with data from peripheral blood, with special emphasis on those cells homing to the gut. Thoracic duct lymph and peripheral blood contained comparable proportions of B and T lymphocytes and CD8+ cells. Thoracic duct lymph contained proportionally more CD4+ cells, more CD4+CD45RO+ that express alpha 4 beta 7 cells and more CD8+CD45RO+ that express alpha 4 beta 7, as compared to peripheral blood. These data suggest an equal recirculation rate of B and T lymphocytes; a more active recirculation of CD4+ cells compared to CD8+ cells; and a more active recirculation of memory cells to the gut as compared to other extra-lymphoid sites in patients under non-inflammatory conditions. Data were also obtained in patients with the system inflammatory response syndrome and multiple organ failure. Although it is generally assumed that granulocytes and monocytes do not recirculate, lymph of multiple organ failure patients contained significantly more granulocytes than monocytes, indicating that in severe generalized inflammatory states these cells re-enter the circulation through the thoracic duct. Furthermore, no increased activation of cells homing to the gut was found in these patients.

Improved technique for cannulation of the murine thoracic duct: a valuable tool for the dissection of immune responses

Several experimental approaches have been used in the past for the cannulation of the thoracic duct in mice. Most, however, are characterized by a modest reproducibility and a low lymph yield. Here, we describe a cannulation technique modified with respect to the anesthesia, the use of a silicone cannula and a simple and efficient intraabdominal fixation of the drain. Surgery averaged 45 min with an intra- and postoperative mortality rate of zero. Postoperatively, mice were given access to an exercise wheel allowing increased mobility and consequently a good lymph flow, thus maintaining the function of the cannula. The mice yielded a mean of 29.3 ml/24 h (range 8-40 ml) thoracic duct lymph, which contained a mean of 2.2 x 10(6) lymphocytes/ml during the first 24 h, decreasing to 0.1 x 10(6) lymphocytes/ml on the 2nd day after cannulation. Patency of the cannulae was 100% after 3 days. Interestingly, we have detected strain dependent differences in the anatomy of the thoracic duct in the mouse and these need to be considered when cannulation procedures are attempted.

Adoptive transfer of immunity induced with chloroquine attenuated Plasmodium yoelii nigeriensis from immune to immunologically naive mice

Immunity was induced in albino mice using Chloroquine-attenuated Plasmodium yoelii nigeriensis which had been maintained under drug pressure in 4 passages. Attempts were made to adoptively transfer immunity from the immune to immunologically naive mice by means of serum, spleen and thoracic duct extracts. None of them conferred complete immunity on the recipients but some protection was gained. This was evident from the prolongation of both the pre-patent periods of the infection and the survival periods of the host mice. The best protection conferred by the different extracts was seen in groups that received 0.4 ml serum, 0.9 ml spleen and 1.2 ml thoracic duct extracts whose survival periods lasted 23, 21 and 15 days respectively as compared to 9 days for the controls.

Lymphocyte adhesive interactions with cultured parotid salivary gland epithelial cells from rats

Cellular interactions control lymphocyte localization within salivary gland tissues and contribute to the immune defense of oral surfaces. We examined lymphocyte adherence to cultured parotid cells using an in vitro assay and found good correlation with previously reported binding to parotid gland frozen sections. Thoracic duct lymphocytes (TDL) bound to parotid cells in greater numbers than thymocytes (74 vs 11 cells/mm2). B cells showed preferential adherence compared to T cells (75% vs 28%). TDL binding was inhibited by sodium azide or cytochalasin B (60% and 80%, respectively). EDTA inhibition (63%) was restored by replacing calcium (9%) but not magnesium (65%). Binding was inhibited by fucoidin or phosphomannan (approximately 70%). Fibronectin peptides had no effect. Culture supernatants were inhibitory for TDL adherence (60%), suggesting that molecules involved in lymphocyte localization may be shed and that parotid cell cultures will be useful for ligand isolation and characterization.

Evidence of post-transcriptional regulation of L-selectin gene expression in rat lymphoid cells

Early investigations of lymphocyte migration in the rat operationally identified a lymphocyte membrane protein, designated 'A.11', which mediates lymphocyte adherence to lymph node (LN) high endothelial venules (HEV). To determine the primary structure of A.11 and examine its expression in lymphoid cells, we constructed an expression phage cDNA library of rat thoracic duct lymphocytes (TDL) and performed screening by immunoselection (utilizing an anti-A.11 polyclonal antiserum) as well as by hybridization selection. We have isolated a approximately 1.6 kb clone, RS-2, and sequencing revealed that it encodes rat L-selectin. The clone contains the complete coding sequence, a 105-bp 5' untranslated region and a 359-bp 3' untranslated region. Transfection of RS-2 cDNA into 70Z/3 cells conferred binding to HEV concomitant with expression of A.11, providing direct evidence that A.11 is rat L-selectin. Metabolic radiolabelling studies revealed that thymocytes synthesize markedly less L-selectin than do TDL or LN lymphocytes. However, Northern blot studies using RS-2 as a probe indicate that thymocytes possess more L-selectin RNA than does TDL. Together, these data provide evidence that post-transcriptional events contribute to regulation of L-selectin expression in thymocytes.

The effect of BCG on thoracic duct lymphocytes

Adoptive immunotherapy is becoming increasingly more important in the management of advanced malignancies. This report describes the results of immunomodulation therapy with BCG in the Dunning tumor. In addition it describes new techniques in the harvesting of lymphocytes. Thoracic duct lymphocytes from 34 rats were evaluated for the effect of the presence of the Dunning R-3327 AT-3 tumor as well as for the response to bacillus Calmette Guerin (BCG). Both tumor and BCG resulted in significant changes in the helper/suppressor T cell ratios.

Synthesis and characterization of rat interleukin-10 (IL-10) cDNA clones from the RNA of cultured OX8- OX22- thoracic duct T cells

A cDNA of the complete coding region of rat IL-10 was cloned and sequenced using RNA isolated from a cultured population of thoracic duct T-lymphocytes obtained from Trichinella spiralis infected animals. The OX8- OX22-T-helper cells were stimulated in vitro with Concanavalin A for 24 hours prior to harvest. Reverse transcription of cellular RNA was primed with oligo-dT followed by amplification of IL-10 specific cDNA by polymerase chain reaction with synthetic oligo nucleotide primers chosen from two highly conserved regions of mouse and human IL-10. The sequence of the coding region of the amplified, cloned rat IL-10 cDNA is 90% identical to the mouse and 82% identical to the human IL-10 cDNA coding regions.

Characterization of cellular and molecular immune effectors against Trichinella spiralis newborn larvae in vivo

The cellular and molecular immune effectors that participated in host immunity against Trichinella spiralis newborn larvae were characterized in vivo using AO rats. Donor rats were immunized with 2,000 muscle larvae orally or 11,400 newborn larvae i.v. Immune serum and cells from spleen, peripheral lymph nodes, mesenteric lymph node, thoracic duct lymph and the peritoneal cavity were obtained from donor rats 10-21 days after infection and transferred into normal recipient rats. The control recipients received either no cells and serum or normal cells and normal serum obtained from normal donors. Newborn larvae (20,000-50,000) were injected either i.v. or ip into these recipients and immunity against newborn larvae was measured either by muscle larvae burden of the recipients three weeks later or by direct recovery of newborn larvae from the peritoneal cavity of the recipients. The experiments demonstrated that immune lymphocytes conferred no protection in the recipients but that immune serum and immune peritoneal cells were protective and these effects were synergistic. Cell adherence to the cuticle and killing of newborn larvae were observed in the peritoneal cavity of immune rats. Positive fluorescence was observed on newborn larvae incubated with fractionated IgM and IgG(E) antibody isotypes. Massive deposition of antibody molecules on newborn larvae was demonstrated by scanning electron microscopy. Studies using transmission electron microscopy revealed that the larval adherent cells were stimulated macrophages, neutrophils and eosinophils.

Characterization of the thoracic duct T-helper cells that co-mediate, with antibody, the rapid expulsion of Trichinella spiralis in adult rats

Thoracic duct cells that act synergistically with immune serum or antibody to transfer rapid expulsion of a challenge infection with Trichinella spiralis muscle larvae were characterized as OX38+, OX8-, OX22- T helper cells. Protective capacity was confined to the dividing T helpers that appeared on days 3-5 in the thoracic duct of rats during a T. spiralis infection. To realize their intestinal priming potential in recipient rats. MHC-compatibility between donor and recipient rat was required. Fractionation of immune serum with 40% saturated ammonium sulphate left transferable protective activity in both the precipitate and supernatant fractions. Absorption of immune serum with muscle larvae antigen removed the capacity to transfer protection.

Mechanisms in passive enhancement of cardiac and renal allografts by serum from liver-grafted rats

The ability of serum from PVG (haplotype RT1c) rats carrying long-term surviving orthotopic DA (RT1a) liver grafts (OLT serum) to enhance cardiac allografts has been confirmed and extended to renal allografts. One millilitre of OLT serum given at the time of allografting was sufficient to cause permanent acceptance of PVG.RT1a heart or kidney grafts in PVG recipients ('enhanced recipients'); the PVG.RT1a being congenic with respect to PVG, and sharing the RT1a haplotype with DA. Adoptive transfer of thoracic duct lymphocytes (TDL) from rats carrying enhanced liver grafts into irradiated recipients indicated that specific alloreactive clones had been functionally inactivated or deleted; this was accompanied by active suppression in which specific alloreactivity of normal TDL was partially inhibited. In vitro, splenic T cells from rats with enhanced grafts mediated allospecific suppression in mixed lymphocyte reaction (MLR). The serum of rats carrying enhanced grafts was able to specifically suppress MLR of the same donor/recipient combination. Thus enhancement by orthotopic liver transplantation (OLT) serum leads to cellular and serological changes in the recipient associated with maintenance of unresponsiveness. Such changes are similar to those seen in liver graft recipients themselves.

T-helper subset function in the gut of rats: differential stimulation of eosinophils, mucosal mast cells and antibody-forming cells by OX8- OX22- and OX8- OX22+ cells

Thoracic duct lymphocytes (TDL) collected 3 days after infection of rats with Trichinella spiralis (TS) and adoptively transferred into normal, uninfected recipients, increased the numbers of both mucosal mast cells (MMC) and eosinophils (EOS) in the intestine. The CD4+ T-helper cell population was separated into two subsets (OX22+ and OX22-) using OX22 monoclonal antibody (mAb) and panning techniques. After adoptive transfer of these T-helper subsets i.v., rats were challenged with TS 24 hr later. The intestine of recipient rats was examined histologically at intervals from Day 3 to Day 21. On Day 9 after transfer, OX22+ T helpers induced a substantial mastocytosis [94 +/- 3, mean +/- SE/villus crypt unit (VCU)], whereas the OX22- T-helper subset increased resident EOS numbers (60 +/- 2/VCU) compared to the challenge control (18 +/- 1 MMC, 27 +/- 1 EOS/VCU). The time of peak eosinophilia was advanced by 3-6 days for recipients of OX22- cells and that of mast cells by 9-12 days for recipients of OX22+ cells. The recipients of OX22-, but not OX22+, cells also showed a large increase in the numbers of B cells in the spleen and mesenteric lymph node (MLN) secreting antibody against adult TS. Recipients of OX22- cells displayed an even increase in EOS throughout the villi, lamina propria (LP) and muscularis, whereas in OX22+ cell recipients mast cells were only present in the lower villus and the epithelium just above the crypt as well as the muscularis layer. Only the CD4+ OX22- cell subset conferred protection against TS in the intestine. We conclude that the OX22+ and OX22- T-helper cells exert distinctive effects in the intestine on MMC and EOS. Because protection was established in the presence of an OX22- T-helper-induced eosinophilia but without a concurrent mastocytosis, the results suggest that MMC are probably not involved in expulsion of TS to terminate the primary infection.

Synergistic interaction between immune serum and thoracic duct cells in the adoptive transfer of rapid expulsion of Trichinella spiralis in adult rats

Rapid expulsion of Trichinella spiralis could be transferred to naive adult rats with thoracic duct lymphocytes and immune serum. Thoracic duct cells collected from Days 3-5 and immune serum collected on Day 28, respectively, after infection were effective. Both cells and serum were unable to transfer rapid expulsion when given alone, even in large volumes. Recipients of immune serum and cells eliminated a significantly higher number of larvae than control rats by 1 hr after challenge with muscle larvae. Rapid expulsion produced 30-80% larval worm rejection but could not be increased by the transfer of more cells or immune serum. Mucus trappings did not appear to play a role in the rejection process. After transfer of 2 x 10(8) cells and 4.0 ml immune serum, rapid expulsion persisted for less than 1 week. However, after adoptive transfer of cells alone, the gut remained functionally receptive to the passive transfer of immune serum for 7 weeks. Therefore, the changes effected by transfer of cells were long lived in contrast to the 1 week, or less, of functional persistence by transferred immune serum. The data indicate that two separate processes, one cell mediated and the other immune serum mediated, interact synergistically in the intestine and lead to the expression of rapid expulsion.

Anti-thoracic duct lymphocyte globulin stimulates human megakaryocytopoiesis in vitro

Anti-thoracic duct lymphocyte globulin (ALG) therapy is effective in patients with aplastic anemia. We examined the effect of ALG on human megakaryocyte progenitor cells (colony-forming unit-megakaryocyte, CFU-Meg) in vitro. Normal human bone marrow mononuclear cells (MNC) were cultured in plasma clots with varying concentrations of ALG or non-immunized horse IgG. After 12 days of culture, significant megakaryocyte colony formation was observed in cultures containing ALG but not in cultures containing non-immunized horse IgG. The peak stimulatory effect seemed to occur with 10-25 micrograms/ml of ALG. When marrow MNC, depleted of adherent and T cells, were cultured in plasma clots with ALG, its stimulatory effect on megakaryocytopoiesis decreased markedly. Finally, it was demonstrated that ALG stimulated marrow MNC to produce a factor stimulatory for CFU-Meg. The in vitro megakaryocytopoietic stimulatory effect of ALG may be related to its clinical efficacy in some patients with aplastic anemia.

Allograft rejection in athymic nude rats by transferred T-cell subsets. I. The response of naive CD4+ and CD8+ thoracic duct lymphocytes to complete allogeneic incompatibilities

PVG.rnu/rnu nude rats were pre-grafted with two allogeneic skin grafts, AO(RTlu) and BN(RTln), 6-14 days in advance of cell transfer. Cellular requirements for rejection were established by transferring graded numbers of B cell-depleted (Ig-) thoracic duct lymphocytes (TDL) or purified W3/25+ (CD4+) or OX8+ (CD8+) TDL subsets. Allografts were rejected by 10(5) to 5 x 10(6) Ig- TDL in a dose-dependent fashion. A similar dose-response relationship was found by transferring 5 x 10(5) to 5 x 10(6) Ig- OX8- TDL (purified by depletion of B cells and OX8+ cells). Larger numbers of Ig- OX8- TDL (10-30 x 10(6)) did not significantly accelerate rejection. W3/25+ TDL alone (10(5)), highly purified by fluorescence-activated cell sorting (FACS), were sufficient to induce allograft rejection in this athymic nude rat model. In contrast, 10 times more FACS purified OX8+ TDL (10(6)) were unable to initiate skin graft rejection despite the complete class I and class II MHC incompatibilities. Furthermore, the addition of 10(6) OX8+ cells did not accelerate or retard the rejection induced by 10(5) W3/25+ cells alone. Pre-grafted nude recipients, irradiated (500 R) 2 hr before W3/25+ TDL injection, in order to eliminate putative nude T cells, rejected allografts on the same day as unirradiated controls. We conclude that when confronted with complete MHC disparities, CD4+ T cells are necessary and sufficient to induce skin allograft rejection whereas CD8+ T cells do not appear to contribute.

Role of intestinal immunization in urinary tract defence

The lack of progress in development of vaccines to stimulate local protection in the urinary tract is attributable in part to the lack of information regarding mechanisms of local immunity and to the difficulty in antigen administration at this site. Experiments reported in this paper indicate that the urinary tract in rats forms part of an effector network linking mucosal organs (the common mucosal immune system). Concomitant immunization of the intestine and urinary tract with ovalbumin resulted in the appearance at both sites of antiovalbumin-containing cells (ACC) of IgA specificity. The gut origin of ACC in the urinary tract was confirmed by demonstrating in similarly immunized rats abrogation of the urinary tract response by chronic drainage of the thoracic lymphatic duct during the post-challenge period and by demonstrating the appearance of radiolabelled ACC in the urinary tract after injection of labelled autologous thoracic duct lymphocytes collected during the post-challenge period. These experiments indicate a role for oral immunization in enhancing the local antibody response in the urinary tract against invading pathogens.

Comparison of antigen uptake by peritoneal macrophages and veiled cells from the thoracic duct using isotope-, FITC-, or gold-labelled antigen

Veiled cells (VC), isolated from the thoracic duct of irradiated lymphadenectomized mice (MLNX) or peritoneal macrophages (PM phi were incubated with isotope-labelled hen egg lysozyme (HEL), purified protein derivative (PPD) or keyhole limpet haemocyanin (KLH) in vitro. About 2-10 times less antigen was associated with VC than with PM phi when measured in a Philips well-type scintillation counter. Autoradiographs of these cells indicated that 3-10% veiled cells had silver grains associated with them in contrast to 20-95% of the PM phi, depending on the type of antigen studied. It was also shown, from the distribution curves for grains in individual cells, that VC contained smaller numbers of grains than PM phi. Transmission electron microscopy using KLH conjugated with colloidal gold and immunofluorescence microscopy using KLH-FITC confirmed the results obtained from autoradiographs. However, measurements of the uptake of KLH-FITC by individual VC and PM phi using flow cytometry indicated that antigen was associated with nearly all VC in vitro but in much smaller amounts than with PM phi. Both VC and PM phi were capable of presenting HEL to primed T lymphocytes in vitro. These results are discussed in relation to the function of VC as accessory cells compared with PM phi.

Intestinal immunity to Trichinella spiralis is a property of OX8- OX22- T-helper cells that are generated in the intestine

The phenotype of T-helper cells conferring protection against Trichinella spiralis (Ts) was studied using adoptive transfer procedures and T-helper cell subsets isolated by monoclonal antibodies. With these techniques OX8- OX22+ and OX8- OX22- T-helper cell populations were isolated from thoracic duct lymph (TDL) of infected rats three-five-fold more concentrated than in unfractionated lymph. The OX8- OX22- cell subset alone transferred enhanced rejection of adult worms from the intestine. The origin of protective OX8- OX22- cells was examined in mesenteric lymphadenectomized (MX) rats. After MX, protective cells were found in the cell population draining directly from the intestine on Days 2-3 after infection. Protective cells first appeared in the mesenteric lymph node (MLN) and efferent lymph at Day 3. MX rats rejected T. spiralis at the same time as intact controls and showed enhanced rejection when immune TDL were transfused. No evidence was found for a direct role of the MLN in the generation or expression of parasite rejection. Depletion of migrating OX8- OX22- blast cells by 48-hr drainage of TDL did not influence the expression of an anamnestic response to challenge infection. This suggests that an intestinally resident cell population has a substantial role in mediating primary worm rejection and anamnestic immunity. Day 2 OX8- OX22- cells from MX rats proliferated in response to the presentation of adult and muscle larvae antigens in vitro. We conclude that protection resides in the OX8- OX22- T-helper cell subset that is produced and functions in the intestine.

The mucosa of the male genital tract; part of the common mucosal secretory immune system?

The selective migration of mucosal-derived lymphoid blasts to other mucosal organs is taken to be an essential part of the common secretory immune system. In rats, proliferating lymphoid cells from mesenteric lymph nodes (mLN) and peripheral lymph nodes (pLN) were labeled in vitro using two different techniques, in order to test the hypothesis that the mucosa of the male genital tract is a preferential site for mLN lymphoid blasts to home to. A low but significant migration to male genital organs was found, but with no difference between blasts from pLN and mLN. Thus there is no evidence to include the male genital tract in the common mucosal secretory immune system. Recirculating lymphocytes from the thoracic duct entered the male genital organs with a similar distribution to the pattern of lymphoid blasts. There is probably an exchange between these immigrating lymphocytes and the different subsets, which are localized in the epithelium (T suppressor) and interstitial tissue (T helper) in male genital organs. The lymphoid cells in the male genital tract might play an important role in the immune function of seminal fluid and in sexually transmissible diseases.

The influence of Peyer's patches on the organ-specific distribution of IgA plasma cells

After the surgical removal of Peyer's patches (PP) in rats, the IgA-containing cells in the thoracic duct, mesenteric lymph nodes and lamina propria of the small intestine are decreased, as shown by immunohistology. The analysis of the immunoglobulin secretion in agar of single-cell suspensions confirmed these results. Using lipopolysaccharide (LPS) 055B5 as antigen, it could be demonstrated that this reduction may be the result of an inadequate presentation of antigen and/or impaired migration of locally primed antigen (AG)-specific cells. The oral application of heat-inactivated Escherichia coli 055B5 to PP-deprived rats resulted almost exclusively in anti-LPS-secreting cells in the mesenteric lymph nodes and spleen, whereas in control animals these cells were distributed along the intestine. Therefore, in rats PP have an important function in the regulation of the intestinal immune responses.

Role of Peyer's patch in the intestinal immune response to cholera toxin in enterically immunized rats

Cholera toxin has been widely used to obtain insight into the cellular dynamics of the antigen-specific mucosal immune response. The present study was undertaken to clarify the influence of the organized intestinal lymphoid tissue (Peyer's patches [PP]) on the distribution of anti-cholera-toxin-containing cells (ACC) after intraperitoneal immunization and intraduodenal challenge with purified cholera toxin. This was done in rats which were surgically deprived of all visible PP. In comparison with sham-operated animals, each PP-deprived rat had nearly the same amount of ACC in the spleen, the mesenteric lymph nodes, and, surprisingly, the thoracic duct lymph. In contrast, the ACC in the duodenum, the jejunum, and the ileum of each PP-deprived animal were drastically reduced. Therefore the PP are suggested as an important organizing structure for the buildup of a local antigen-specific immune response.

Distribution and functional characteristics of antigen-specific helper T cells arising after Peyer's patch immunization

Antigen-specific T-helper cells for IgA responses arise in Peyer's patches (PP) following their immunization by subserosal injection of keyhole limpet haemocyanin (KLH). These are of the W3/25 phenotype and the W3/25 receptor is shown here to be involved in their helper function. These cells originate in PP and migrate via mesenteric lymph nodes (MLN) to thoracic duct lymph, although the MLN appear to be unnecessary for the induction or maturation of antigen-specific helper cells collected in thoracic duct lymph after intra-Peyer's patch (i.p.p.) immunization. KLH-specific helper cells can be detected subsequently in the intraepithelial lymphocyte population and also among lamina propria lymphocytes. The helper cells also relocate to PP distant to their site of origin where they are retained only when antigen is present. While i.p.p. immunization is an efficient route for the induction of IgA helper cells in gut-associated lymphoid tissue, it differs from oral immunization in that concomitant induction of antigen-specific splenic suppressor cells does not occur, indicating a role for epithelial antigen processing in this phenomenon.

Characterization of a cell population in thoracic duct lymph that adoptively transfers rejection of adult Trichinella spiralis to normal rats

In Trichinella spiralis-infected rats, a population of cells in thoracic duct lymph (TDL) that can adoptively transfer protection to naive rats was identified and characterized. During the course of T. spiralis infection, blast cells appeared in lymph from Day 3-4, and only Day 3-4 TDL cells had protective properties after transfer. Protection was evident in a 1-2-day increase in the slow rejection of adult worms beginning 8-9 days after the challenge infection. The minimum number of TDL cells capable of transferring protection was 1.8 X 10(8) cells. Transferred cells could protect against a challenge infection with adult worms alone. A double cross-over experiment demonstrated that major histocompatibility complex identity was essential for effective transfer of protection (MHC restriction). An experiment using the mitotic inhibitor vinblastine showed that the protective cells belonged to a dividing cell population. The phenotype of the protective TDL was confirmed by a two-step cell separation procedure. First, it was demonstrated that surface Ig- cells (T cells) separated by affinity chromatography could transfer protection. Second, these surface Ig- cells were divided into two subpopulations by panning using monoclonal antibodies OX-8 and W3/25. The results showed that W3/25+ or OX-8- cells (T-helper) were effective in transferring protection. Protection was only seen when rats adoptively transferred with cells were challenged 1 day after cell transfer.

The effects of interferon on the recirculation of lymphocytes in the rat

Lymphocytes from the thoracic duct (TDL) were incubated with interferon (IFN) prior to i.v. injection into syngeneic or allogeneic recipient rats. The effect of IFN treatment on the ability of lymphocytes to migrate was studied using 'standard' TDL collected overnight at 4 degrees or an 'optimal' collection of passaged TDL which recirculate with an accelerated tempo (Smith & Ford, 1983). Interferon treatment resulted in an increase in early (30 min) localization of both standard and optimal TDL into lymph nodes. Entry of standard IFN-treated TDL was increased by 91% and 54% in cervical and mesenteric lymph nodes, respectively; increases of 50% and 22% in the same lymph nodes were recorded for optimal IFN-treated TDL. Enhanced entry of standard TDL was contrasted with a reduced ability of IFN-treated TDL to migrate out of lymph nodes; there was a reduced output into the thoracic duct and a surplus of IFN-treated lymphocytes in cervical lymph nodes despite 24 hr continuous thoracic duct drainage. Incubation with interferon did not, however, alter the ability of optimal TDL to reach the thoracic duct rapidly after injection. Allogeneic lymphocytes, which are eliminated soon after injection by an NK-like cytotoxicity, a phenomenon termed ALC, were unaffected by incubation with interferon, thus IFN-treated allogeneic lymphocytes were killed after i.v. injection as rapidly as untreated cells.

Vascular endothelial markers of the human thoracic duct and lacteal

Factor VIII-related antigen (F8) and Ulex europaeus lectin (UEL) are accepted markers for human blood vessel endothelium. However, disagreement exists as to whether lymphatic vessels stain for F8, and accordingly this study was undertaken to address this issue. Moreover, another vascular endothelial marker, angiotensin converting enzyme (ACE) was also examined in lymphatics. Segments of human thoracic duct and portions of small bowel containing lacteals with post-mortem intervals of less than 15 hours, were removed at autopsy and fixed in B5 or formalin. The specimens were processed routinely and sections examined by indirect immunohistochemical techniques for F8 (Dako Corp.), ACE and for UEL (EY Lab). F8, UEL, and ACE positivity was uniformly found in thoracic ducts and lacteals; however, the staining intensity was less in lymphatic vessels with F8 and UEL than with comparable arteries or veins. ACE staining intensity, on the other hand, was similar in blood vessels and lymphatics. Both formalin and B5 fixation preserved antigenicity; however, background staining was greater with B5 fixation whereas tissue staining was slightly more intense with formalin fixation.

A study of the role of cell-mediated immunity in bluetongue virus infection in sheep, using cellular adoptive transfer techniques

The transfer of thoracic duct lymphocytes from sheep inoculated 14 days, but not 7 days previously with bluetongue virus into their monozygotic twin resulted in some protection from challenge with bluetongue virus. T cell enrichment of the 14 day thoracic duct lymphocyte population resulted in a similar effect, indicating the T cell basis of the observed protection. Animals recovered from infection with bluetongue virus type 3 and which received thoracic duct lymphocytes from an identical twin recently infected with the same bluetongue virus type were protected from challenge with bluetongue type 4. These observations suggest that T lymphocytes play an important role in protection against bluetongue virus.

Characterization of recirculating lymphocytes in rheumatoid arthritis patients: selective deficiency of natural killer cells in thoracic duct lymph

Five patients with rheumatoid arthritis (RA), who were treated by lymphocyte depletion by using thoracic duct drainage (TDD), provided an opportunity to characterize the phenotype and function of their recirculating lymphocytes. We found that: a) thoracic duct lymphocytes (TDL) were similar in their proportion of T cells (83% +/- 6 OKT3+), OKT4+ subset (65% +/- 8), and OKT8+ subset (22% +/- 6) to peripheral blood lymphocytes (PBL): b) fewer natural killer-like cells were present in TDL (5% +/- 4 Leu-7+; 2% +/- 2 Leu-11+: 8% +/- 2 OKM -1+) than in PBL (20% +/- 10 Leu-7+: 11% +/- 6 Leu-11+; 18% +/- 5 OKM -1) (p less than 0.01); c) TDL differed from synovial fluid lymphocytes ( SFL ) and synovial membrane lymphocytes ( SML ) in that TDL lacked a high percentage of activated lymphocytes (T cells bearing Ia antigen, OKT10 , and transferrin receptor): d) immature T cells (expressing either OKT6 antigen or reactive with peanut agglutinin) were not found in TDL even late in the course of TDD: and e) in vitro functional studies demonstrated that TDL were similar to PBL in their ability to synthesize immunoglobulin after mitogen stimulation and to generate cytotoxic T lymphocytes capable of lysing autologous EBV-transformed B cells. However, natural killer activity, as measured by lysis of K562 cells was significantly lower in TDL than PBL (p less than 0.05). These results demonstrate that natural killer cells defined by phenotype and function are excluded from thoracic duct lymph and thus have a circulation pattern different from most T cells.

Antithoracic duct lymphocyte globulin therapy of severe aplastic anemia

We performed a prospective randomized trial of antithoracic duct lymphocyte globulin (ATDLG), HLA-haploidentical marrow, and androgen (regimen ABA) versus androgen alone (concurrent STANDARD care controls) in 42 newly diagnosed individuals with severe aplastic anemia. ABA patients also were matched with patients from our preceding study (historical STANDARD care controls). Supportive care and pretreatment patient characteristics were the same in all groups. By life table analysis, 76% of patients receiving ABA are alive at 2 yr compared to 31% of the concurrent control group (p less than 0.002 versus ABA) and 19% of the historical controls (p less than 0.0001 versus ABA) given STANDARD care. ABA patients had greater hematologic improvement than either control group (p less than 0.001). However, improvement with ABA was often incomplete. Toxicity of ATDLG was considerable but manageable. Further studies to determine the mechanism of action and active component(s) of ABA are indicated.

The migration of lymphocytes across specialized vascular endothelium. VI. The migratory behaviour of thoracic duct lymphocytes retransferred from the lymph nodes, spleen, blood, or lymph of a primary recipient

Thoracic duct lymphocytes labelled with 51Cr were injected into a primary recipient and then were transferred for a second time from the lymph nodes (cervical and/or mesenteric), spleen, lymph, or blood into a series of final recipients. Measurement of the organ distribution of labelled lymphocytes in the final recipients enabled three main conclusions to be drawn. (1) Lymphocytes that had localized in the spleen, mesenteric lymph nodes (LN), or cervical LN of the first recipient showed no tendency to return in increased numbers to the same organ in the final recipient. (2) Lymphocytes that had recently entered the spleen or LN were temporarily impaired in their ability to reenter LN. This capacity was recharged when the cells returned to the lymph and the blood. (3) Lymphocytes that had been passaged from blood to lymph and collected for up to 4 hr at room temperature entered the LN of a recipient much faster than did nonpassaged thoracic duct lymphocytes collected overnight at 0 degree C. Supplementary experiments indicated that the different migratory behavior of thoracic duct lymphocytes under these two circumstances was mainly a consequence of their handling in vitro during the collecting and the labelling procedures. This functional impairment was not associated with a diminished ability to enter the spleen and bone marrow or to survive in recipients for up to 24 hr.

Analytical and functional studies on the T cells of untreated and immunologically tolerant diabetes-prone BB rats

Lymphocyte profiles of untreated diabetes-prone BB rats (BBDP) and their normal marrow-inoculated tolerant littermates were determined with the aid of a fluorescence-activated cell sorter by using monoclonal antibodies specific for rat T cell (W3/13) and T cell subsets (W3/25, T helper; OX8, T cytotoxic/suppressor). In contrast to non-diabetes-prone rats and to their marrow-inoculated littermates, untreated BBDP rats were found to be T lymphocytopenic with reduced W3/25+ cells and with a major loss of OX8+ cells. Moreover, their lymphocytes displayed depressed alloreactivity that was not restored by addition of exogenous IL 2.

Effect of interferon on thoracic duct lymphocyte output: induction with either poly I:poly C or vaccinia virus

Systemic inoculation of the interferon (IFN) inducer polyinosinic-polycytidylic polyribonucleotide (poly I:poly C) into CBA/J mice produces a significant decrease in the number of thoracic duct lymphocytes (TDL) collected 6 to 22 hr after injection. The number of TDL is restored to normal levels by 48 to 64 hr. Residual TDL collected during the inhibition period of poly I:poly C treatment showed a phenotypic profile similar to phosphate-buffered saline- (PBS) treated control groups when examined for Lyt-1.1, Lyt-2, Thy-1.2 and Iak surface markers. Interferon is implicated as the mediator of this phenomenon since: 1) Inoculation of exogenous IFN can induce a similar suppression in the number of recoverable TDL. 2) Pretreatment of mice with sheep anti-murine IFN serum can block this effect of poly I:poly C. Similar experiments with vaccinia virus demonstrate that although live virus can partially suppress the TDL output, almost complete suppression is achieved with ultraviolet (UV)-inactivated virus. Vaccinia virus-induced suppression of the number of TDL also appears to be caused by IFN since: 1) UV-inactivated virus induces significantly higher serum levels of IFN in comparison to live virus. 2) The suppression of TDL output by either live or UV-inactivated vaccinia virus can be blocked by pretreatment with anti-murine IFN. These findings suggest that the immunosuppression often associated with viral infections may be at least partially due to a decrease in lymphocyte recirculation mediated by the IFN initially released in response to the virus.

The effect of intravenous Corynebacterium parvum on gut associated mononuclear phagocytes in normal and tumour bearing rats

Corynebacterium Parvum, which has been used in the treatment of human colorectal cancer, probably exerts its action through cells of the mononuclear phagocyte system (MPS). In this study the effect of systemically administered C. parvum has been measured on gut associated MPS cells in normal and colorectal cancer bearing rats. MPS cells are not normally found in samples of lymph obtained after cannulation of the thoracic duct (TDC). However, after total extirpation of the mesenteric lymph nodes, TDC yields samples in which up to 5% of the total cell population appear to be MPS cells. This procedure has been carried out in adult Wistar rats enabling an in vivo study to be made on the effect of C. parvum treatment on the effluent gut cells. Measurements have been made both of the number of cells found in thoracic duct lymph and of their capacity to phagocytose sensitized sheep red blood cells. These measurements were repeated in a mesenteric lymphadenectomized group of rats which had also undergone induction of colonic cancer using dimethylhydrazine. C. parvum treatment did not effect total cell, or phagocyte numbers in thoracic duct lymph (TDL). However rats with colonic cancers showed a marked reduction in the numbers of phagocytic cells in TDL irrespective of C. parvum treatment.

Antigen transport. I. Demonstration and characterization of cells laden with antigen in thoracic duct lymph and blood

Thoracic duct lymph (TDL) of nonimmune rats and mice was examined for the presence of antigen-carrying cells immediately following a single injection of 125I-labelled or fluorescence-labelled serum protein antigens. Small numbers of cells laden with antigen (approximately 1/2000 to 1/5000) were identified in TDL and blood by autoradiography or fluorescence microscopy. The antigen-laden (Ag-L) cells resembled macrophages in that a large number adhered to plastic, they phagocytosed bacteria or a particulate dye, were non-specific esterase positive, radioresistant and could take up more than one antigen at one time in vivo. Surface phenotyping using monoclonal antibodies against rat cell markers established that Ag-L cells did not express Ia determinants. The results suggest the existence of a subpopulation of macrophage-related cells that may be involved in the transport of antigen and in stimulation of antibody responses.

The response of the foetal lamb to maternal lymphocytes

Foetal lambs were inoculated with either maternal or third-party lymphocytes. Of foetuses transfused in the first half of pregnancy (from 49 to 73 days), one quarter survived until the fifth month. Examination of the immunological reactivity of these survivors revealed that all rejected skin grafts from the lymphocyte donors and manifested normal mixed lymphocyte reactivity. In two instances, responsiveness of the transfused lambs to normal lymphocyte transfer was reduced. Foetal lambs transfused with large numbers of maternal lymphocytes in the last third of pregnancy could survive provided the donor ewe had not been sensitized against foetal or paternal determinants. Following intravenous challenge with maternal lymphocytes, cells collected over a prolonged period from the thoracic duct of the foetal recipient exhibited depression of anti-maternal reactivity in mixed lymphocyte culture.