MAdCAM-1 expressing sacral lymph node in the lymphotoxin beta-deficient mouse provides a site for immune generation following vaginal herpes simplex virus-2 infection

Immunotherapy that leverages HPV-specific immune responses for precancer lesions of cervical cancer

Cervical cancer and its precursor lesion, cervical intraepithelial neoplasia (CIN), are caused by high-risk human papillomavirus (HPV) viral infection and are highly susceptible to host immunity targeting of HPV viral proteins, which include both foreign antigens and cancer antigens expressed by tumors. Immunotherapy that induces Th1 immunoreactivity against viral proteins is expected to take advantage of this immunological regression mechanism. However, although cancer immunotherapies for cervical cancer and CIN have been developed over the past several decades, none have been commercialized. Most of these immunotherapies target the viral cancer proteins E6 and E7, which are generally the same. The reasons for the underdevelopment of HPV-targeted immunotherapy differ depending on whether the target is invasive cancer or CIN. We here summarize the developmental history of cancer immunotherapy for CIN and discuss strategies for solving the problems that led to this underdevelopment. We note that CIN is a mucosal lesion and propose that inducing mucosal immunity may be the key.

Regulation, Maintenance, and Remodeling of High Endothelial Venules in Homeostasis, Inflammation, and Cancer

High endothelial venules (HEVs), high walled cuboidal blood vessels, through their expression of adhesion molecules and chemokines, allow the entrance of lymphoid cells into primary, secondary, and tertiary lymphoid structures (aka tertiary lymphoid organs). HEV heterogeneity exists between various lymphoid organs in their expression of peripheral node addressin (PNAd) and mucosal vascular addressin adhesion molecule 1(MAdCAM-1). Transcriptomic analyses reveal extensive heterogeneity, plasticity, and regulation of HEV gene expression in ontogeny, acute inflammation, and chronic inflammation within and between lymphoid organs. Rules regulating HEV development are flexible in inflammation. HEVs in tumor tertiary lymphoid structures are diagnostic of favorable clinical outcome and response to Immunotherapy, including immune check point blockade. Immunotherapy induces HEVs and provides an entrance for naïve, central memory, and effector cells and a niche for stem like precursor cells. Understanding HEV regulation will permit their exploitation as routes for drug delivery to autoimmune lesions, rejecting organs, and tumors.

Lymphotoxin and TNF: how it all began-a tribute to the travelers

The journey from the discoveries of lymphotoxin (LT) and tumor necrosis factor (TNF) to the present day age of cytokine inhibitors as therapeutics has been an exciting one with many participants and highs and lows; the saga is compared to that in "The Wizard of Oz". This communication summarizes the contributions of key players in the discovery of the cytokines and their receptors, the changes in nomenclature, and the discovery of the LT family's crucial role in secondary and tertiary lymphoid organs. The remarkable advances in therapeutics are detailed as are remaining problems. Finally, special tribute is paid to two pioneers in the field who have recently passed away: Byron H. Waksman and Lloyd Old.

Diet-induced obesity may affect the uterine immune environment in early-mid pregnancy, reducing NK-cell activity and potentially compromising uterine vascularization

OBJECTIVES

To investigate the effect of obesity in early-mid pregnancy on crucial pregnancy hormones and the uterine immune environment.

BACKGROUND

Obesity impacts reproductive ability, adversely affecting conception and leading to complications in pregnancy. Obesity is often regarded as a stress state and an immune disease, both of which may contribute to pregnancy failure. We previously demonstrated that stress in early pregnancy greatly alters progesterone secretion. As progesterone is an immunomodulator, altered progesterone secretion may adversely modify the maternal immune system. In the current study, we test the hypothesis that obesity during pregnancy adversely alters the uterine immune environment.

METHODS

An obese mouse model was created by feeding C57/BL6 mice on a high-fat (HF)/sugar diet for 12 weeks before pregnancy. Control mice were fed on lower-fat/sugar chow. Mice were mated, and on day 7.5 of pregnancy plasma progesterone and prolactin were measured by immunoassay. Cells from the uterus-draining inguinal lymph nodes were collected for analysis of the uterine immune response by flow cytometry.

RESULTS

Diet-induced obesity increased the secretion of progesterone and altered a number of uterine natural killer (NK)- and T-cell responses. These included a marked reduction in the percentage of leucocyte-derived NK cells and reduced expression of interferon-γ (IFN-γ) in the NK cells compared with control mice.

CONCLUSIONS

Maternal obesity, induced by an HF diet, may lead to a reduction in the expression of IFN-γ in NK cells. NK-cell-derived IFN-γ is reported to be involved in supporting uterine spiral artery remodelling. Thus, obesity in early pregnancy may compromise vascularization by reducing the expression of IFN-γ-positive NK cells. Furthermore, the expression of uterine CD8(+) cells was reduced in the HF diet-fed mice, suggesting obesity may adversely alter the maternal immune adaptation that is essential for effective pregnancy.

Myxomavirus-derived serpin prolongs survival and reduces inflammation and hemorrhage in an unrelated lethal mouse viral infection

Lethal viral infections produce widespread inflammation with vascular leak, clotting, and bleeding (disseminated intravascular coagulation [DIC]), organ failure, and high mortality. Serine proteases in clot-forming (thrombotic) and clot-dissolving (thrombolytic) cascades are activated by an inflammatory cytokine storm and also can induce systemic inflammation with loss of normal serine protease inhibitor (serpin) regulation. Myxomavirus secretes a potent anti-inflammatory serpin, Serp-1, that inhibits clotting factor X (fX) and thrombolytic tissue- and urokinase-type plasminogen activators (tPA and uPA) with anti-inflammatory activity in multiple animal models. Purified serpin significantly improved survival in a murine gammaherpesvirus 68 (MHV68) infection in gamma interferon receptor (IFN-γR) knockout mice, a model for lethal inflammatory vasculitis. Treatment of MHV68-infected mice with neuroserpin, a mammalian serpin that inhibits only tPA and uPA, was ineffective. Serp-1 reduced virus load, lung hemorrhage, and aortic, lung, and colon inflammation in MHV68-infected mice and also reduced virus load. Neuroserpin suppressed a wide range of immune spleen cell responses after MHV68 infection, while Serp-1 selectively increased CD11c(+) splenocytes (macrophage and dendritic cells) and reduced CD11b(+) tissue macrophages. Serp-1 altered gene expression for coagulation and inflammatory responses, whereas neuroserpin did not. Serp-1 treatment was assessed in a second viral infection, mouse-adapted Zaire ebolavirus in wild-type BALB/c mice, with improved survival and reduced tissue necrosis. In summary, treatment with this unique myxomavirus-derived serpin suppresses systemic serine protease and innate immune responses caused by unrelated lethal viral infections (both RNA and DNA viruses), providing a potential new therapeutic approach for treatment of lethal viral sepsis.

Delayed but effective induction of mucosal memory immune responses against genital HSV-2 in the absence of secondary lymphoid organs

To examine whether local immunization in the absence of secondary lymphoid organs (SLOs) could establish effective antiviral memory responses in the female genital tract, we examined immunity in the vaginal tracts of LTα-/- mice, LTα-/- SPL (splenectomized), and control C57BL/6 (WT) mice. All three groups of mice were immunized intravaginally (IVAG) with attenuated thymidine kinase-negative (TK(-)) Herpes simplex virus type 2 (HSV-2) and challenged 4-6 weeks later with wild-type (WT) HSV-2. Both groups of LTα-/- mice exhibited delayed viral clearance and prolonged genital pathology after immunization. Following IVAG WT HSV-2 challenge, LTα-/- and LTα-/- SPL mice had significantly lower levels of HSV-2-specific IgG and IgA in the vaginal secretions. Although the frequency of B and T cells in the vaginal mucosa was comparable or higher in both groups of LTα-/- mice, lower frequency of HSV-2-specific interferon-γ (IFNγ)-producing CD3+ T cells was seen after immunization and after challenge, compared with WT group. Despite this, immunized mice in all three groups showed complete sterile protection against IVAG WT HSV-2 challenge. These results show that even in the absence of SLOs, IVAG immunization generates effector memory immune responses at genital mucosa that can provide antiviral protection against subsequent viral exposures. This will inform new strategies to design mucosal vaccines against sexually transmitted infections.

A vaccine strategy that protects against genital herpes by establishing local memory T cells

The majority of successful existing vaccines rely on neutralizing antibodies, which may not require specific anatomical localization of B cells. However, efficacious vaccines that rely on T cells for protection have been difficult to develop, as robust systemic memory T cell responses do not necessarily correlate with host protection¹. In peripheral sites, tissue-resident memory T cells provide superior protection compared to circulating memory T cells^2,3. Here, we describe a simple and non-inflammatory vaccine strategy that enables the establishment of a protective memory T cell pool within peripheral tissue. The female genital tract, which is a portal of entry for sexually transmitted infections (STIs), is an immunologically restrictive tissue that prevents entry of activated T cells in the absence of inflammation or infection⁴. To overcome this obstacle, we explored a vaccine strategy we term “prime and pull” to establish local tissue-resident memory T cells at a site of potential viral exposure. This approach relies on two steps: 1) conventional parenteral vaccination to elicit systemic T cell responses (prime), followed by 2) recruitment of activated T cells via topical chemokine application to the restrictive genital tract (pull), where such T cells establish a long-term niche and mediate protective immunity. Prime and pull protocol reduces the spread of infectious HSV-2 into the sensory neurons and prevents development of clinical disease. These results reveal a promising vaccination strategy against HSV-2, and potentially against other STIs such as HIV-1.

Regional and mucosal memory T cells

After infection, most antigen-specific memory T cells reside in nonlymphoid tissues. Tissue-specific programming during priming leads to directed migration of T cells to the appropriate tissue, which promotes the development of tissue-resident memory in organs such as intestinal mucosa and skin. Mechanisms that regulate the retention of tissue-resident memory T cells include transforming growth factor-β (TGF-β)-mediated induction of the E-cadherin receptor CD103 and downregulation of the chemokine receptor CCR7. These pathways enhance protection in internal organs, such as the nervous system, and in the barrier tissues--the mucosa and skin. Memory T cells that reside at these surfaces provide a first line of defense against subsequent infection, and defining the factors that regulate their development is critical to understanding organ-based immunity.

HSV-2 infection of dendritic cells amplifies a highly susceptible HIV-1 cell target

Herpes simplex virus type 2 (HSV-2) increases the risk of HIV-1 infection and, although several reports describe the interaction between these two viruses, the exact mechanism for this increased susceptibility remains unclear. Dendritic cells (DCs) at the site of entry of HSV-2 and HIV-1 contribute to viral spread in the mucosa. Specialized DCs present in the gut-associated lymphoid tissues produce retinoic acid (RA), an important immunomodulator, able to influence HIV-1 replication and a key mediator of integrin α₄β₇ on lymphocytes. α₄β₇ can be engaged by HIV-1 on the cell-surface and CD4⁺ T cells expressing high levels of this integrin (α₄β₇^high) are particularly susceptible to HIV-1 infection. Herein we provide in-vivo data in macaques showing an increased percentage of α₄β₇^high CD4⁺ T cells in rectal mucosa, iliac lymph nodes and blood within 6 days of rectal exposure to live (n = 11), but not UV-treated (n = 8), HSV-2. We found that CD11c⁺ DCs are a major target of HSV-2 infection in in-vitro exposed PBMCs. We determined that immature monocyte-derived DCs (moDCs) express aldehyde dehydrogenase ALDH1A1, an enzyme essential for RA production, which increases upon HSV-2 infection. Moreover, HSV-2-infected moDCs significantly increase α₄β₇ expression on CD4⁺ T lymphocytes and HIV-1 infection in DC-T cell mixtures in a RA-dependent manner. Thus, we propose that HSV-2 modulates its microenviroment, influencing DC function, increasing RA production capability and amplifying a α₄β₇^highCD4⁺ T cells. These factors may play a role in increasing the susceptibility to HIV-1.

The vast majority of HIV-1 infections occur through genital and rectal mucosa. A better understanding of the characteristics of the mucosal microenvironment that help HIV-1 replication is critical to developing strategies for prevention of HIV-1 transmission. HSV-2 infects genital and rectal mucosa and infected individuals carry an increased risk for HIV-1 infection. Clarifying the mechanisms involved in the increased susceptibility of HSV-2 positive individuals to HIV-1 infection may help understating the characteristics of mucosal microenvironment that facilitate HIV-1 transmission. We previously described a specific interaction between HIV-1 and integrin α₄β₇, a signature molecule that allows lymphocytes to gain access to the gut tissue, a major site of HIV-1 replication. Vitamin A and its metabolite, retinoic acid, have an important role in balancing the immune response in the gut and in the expression of integrin α₄β₇. Here we describe that HSV-2 rectal infection in monkeys increases the frequency of α₄β₇⁺ CD4⁺ T cells in blood and rectal tissue and that this could be at least partially explained by the ability of HSV-2 infected DCs to secrete retinoic acid and up-regulate α₄β₇ on CD4⁺ T cells. These phenomena could be responsible for increasing HIV-1 replication in DC-T cell co-cultures.

Retinoic acid as a vaccine adjuvant enhances CD8+ T cell response and mucosal protection from viral challenge

Vaccine-induced memory T cells localized at mucosal sites can provide rapid protection from viral infection. All-trans-retinoic acid (ATRA) has been shown to act physiologically to induce the expression of gut-homing receptors on lymphocytes. We tested whether the administration of exogenous ATRA during a systemic vaccination of mice could enhance the generation of mucosal CD8(+) T cell immunity, which might represent a strategy for establishing better protection from viral infection via mucosal routes. ATRA induced the expression of CCR9 and α4β7 on both mouse and human CD8(+) T cells activated in vitro. The administration of ATRA to mice during in vivo priming with a replication-defective recombinant adenovirus vector expressing the lymphocytic choriomeningitis virus glycoprotein (LCMVgp) (Ad5gp) increased numbers of both effector and memory T cells in intestinal mucosal tissues and showed higher frequencies of systemic central memory-like T cells that exhibited enhanced proliferation during boosting immunization with recombinant modified vaccinia virus Ankara expressing LCMVgp (MVAgp). Mice that received ATRA during Ad5gp vaccination were more resistant to intravaginal challenge by recombinant vaccinia virus expressing LCMVgp (VVgp), reflecting in part stronger T cell recall responses in situ. Thus, ATRA appears to be useful as an adjuvant during vaccination to increase memory T cell responses and protection from viral infection at mucosal sites and may facilitate the development of more effective vaccines against mucosally transmitted pathogens such as HIV.

Role of gut-resident dendritic cells in inflammatory bowel disease

The gastrointestinal immune system, innate and adaptive, is continuously exposed to challenges provided by the enteric flora. In most cases, the result of mucosal immune responses is the development of tolerance. Mucosal dendritic cells initiate and regulate local immune responses. Uncontrolled local immune responses are thought to be a major factor in the development of inflammatory bowel disease, such as Crohn's disease and ulcerative colitis. This review will discuss the function of dendritic cells in the recognition of the enteric flora and their role in the development of intestinal inflammation.

Secondary lymphoid organs: responding to genetic and environmental cues in ontogeny and the immune response

Secondary lymphoid organs (SLOs) include lymph nodes, spleen, Peyer's patches, and mucosal tissues such as the nasal-associated lymphoid tissue, adenoids, and tonsils. Less discretely anatomically defined cellular accumulations include the bronchus-associated lymphoid tissue, cryptopatches, and isolated lymphoid follicles. All SLOs serve to generate immune responses and tolerance. SLO development depends on the precisely regulated expression of cooperating lymphoid chemokines and cytokines such as LTalpha, LTbeta, RANKL, TNF, IL-7, and perhaps IL-17. The relative importance of these factors varies between the individual lymphoid organs. Participating in the process are lymphoid tissue initiator, lymphoid tissue inducer, and lymphoid tissue organizer cells. These cells and others that produce crucial cytokines maintain SLOs in the adult. Similar signals regulate the transition from inflammation to ectopic or tertiary lymphoid tissues.

Role of mucosal dendritic cells in inflammatory bowel disease

The gastrointestinal innate and adaptive immune system continuously faces the challenge of potent stimuli from the commensal microflora and food constituents. These local immune responses require a tight control, the outcome of which is in most cases the induction of tolerance. Local T cell immunity is an important compartment of the specific intestinal immune system. T cell reactivity is programmed during the initial stage of its activation by professional presenting cells. Mucosal dendritic cells (DCs) are assumed to play key roles in regulating immune responses in the antigen-rich gastrointestinal environment. Mucosal DCs are a heterogeneous population that can either initiate (innate and adaptive) immune responses, or control intestinal inflammation and maintain tolerance. Defects in this regulation are supposed to lead to the two major forms of inflammatory bowel disease (IBD), Crohn’s disease (CD) and ulcerative colitis (UC). This review will discuss the emerging role of mucosal DCs in regulating intestinal inflammation and immune responses.

Nonmucosal alphavirus vaccination stimulates a mucosal inductive environment in the peripheral draining lymph node

The strongest mucosal immune responses are induced following mucosal Ag delivery and processing in the mucosal lymphoid tissues, and much is known regarding the immunological parameters which regulate immune induction via this pathway. Recently, experimental systems have been identified in which mucosal immune responses are induced following nonmucosal Ag delivery. One such system, footpad delivery of Venezuelan equine encephalitis virus replicon particles (VRP), led to the local production of IgA Abs directed against both expressed and codelivered Ags at multiple mucosal surfaces in mice. In contrast to the mucosal delivery pathway, little is known regarding the lymphoid structures and immunological components that are responsible for mucosal immune induction following nonmucosal delivery. In this study, we have used footpad delivery of VRP to probe the constituents of this alternative pathway for mucosal immune induction. Following nonmucosal VRP delivery, J chain-containing, polymeric IgA Abs were detected in the peripheral draining lymph node (DLN), at a time before IgA detection at mucosal surfaces. Further analysis of the VRP DLN revealed up-regulated alpha4beta7 integrin expression on DLN B cells, expression of mucosal addressin cell adhesion molecule 1 on the DLN high endothelia venules, and production of IL-6 and CC chemokines, all characteristics of mucosal lymphoid tissues. Taken together, these results implicate the peripheral DLN as an integral component of an alternative pathway for mucosal immune induction. A further understanding of the critical immunological and viral components of this pathway may significantly improve both our knowledge of viral-induced immunity and the efficacy of viral-based vaccines.

Monitoring of vaccine-specific gamma interferon induction in genital mucosa of mice by real-time reverse transcription-PCR

Monitoring of T-cell responses in genital mucosa has remained a major challenge because of the absence of lymphoid aggregates and the low abundance of T cells. Here we have adapted to genital tissue a sensitive real-time reverse transcription-PCR (TaqMan) method to measure induction of gamma interferon (IFN-gamma) mRNA transcription after 3 h of antigen-specific activation of CD8 T cells. For this purpose, we vaccinated C57BL/6 mice subcutaneously with human papillomavirus type 16 L1 virus-like particles and monitored the induction of CD8 T cells specific to the L1(165-173) H-2D(b)-restricted epitope. Comparison of the responses induced in peripheral blood mononuclear cells and lymph nodes (LN) by L1-specific IFN-gamma enzyme-linked immunospot assay and TaqMan determination of the relative increase in L1-specific IFN-gamma mRNA induction normalized to the content of CD8b mRNA showed a significant correlation, despite the difference in the readouts. Most of the cervicovaginal tissues could be analyzed by the TaqMan method if normalization to glyceraldehyde-3-phosphate dehydrogenase mRNA was used and a significant L1-specific IFN-gamma induction was found in one-third of the immunized mice. This local response did not correlate with the immune responses measured in the periphery, with the exception of the sacral LN, an LN draining the genital mucosa, where a significant correlation was found. Our data show that the TaqMan method is sensitive enough to detect antigen-specific CD8 T-cell responses in the genital mucosa of individual mice, and this may contribute to elaborate effective vaccines against genital pathogens.

Prostaglandin E2 modulates dendritic cell function during chlamydial genital infection

Inflammatory responses mediated by antigen-presenting dendritic cells (DCs), can be modulated by the presence of prostaglandins (PG), including prostaglandin E2 (PGE2). PGE2 modifies the production of an immune response by altering DC function through PGE2 receptors. PGE2 is produced by epithelial cells lining the murine female reproductive tract during Chlamydia muridarum infection and likely manipulates the antichlamydial immune response during antigen uptake in the genital mucosa. Our data demonstrate that the PGE2 present locally in the genital tract upon chlamydial genital infection enhanced the recruitment of CD11b+ conventional DCs, but not CD45R+ plasmacytoid DCs, to infected genital tract tissue and draining lymph nodes in vivo. Furthermore, exposure to PGE2 in vitro during infection of murine bone-marrow-derived conventional DCs (cDCs) boosted interleukin-10 mRNA and protein while not influencing interleukin-12p40 production. Infection of cDCs markedly increased mRNA production of the costimulatory molecules CD86, CD40 and a member of the C-type lectin family, DEC-205, but addition of PGE2 increased other costimulatory molecules and C-type lectins. Also, exposure of PGE2 to infected cDCs increased FcgammaRIII and FcgammaRIIb, suggesting that PGE2 enhances the uptake and presentation of C. muridarum and augments production of the antichlamydial adaptive immune response. Taken together, the data suggest that exposure of infected cDCs to PGE2 drives production of a diverse adaptive immune response with implications for regulating tissue inflammation.

Mucosal dendritic cells

The internal surfaces of the human body are covered by distinct types of epithelial cells and mucus-secreting cells. The mucosal surfaces serve many vital functions, such as respiration (nasal passage and lung), absorption (gastrointestinal tract), excretion (lung, urinary tract, large intestine), and reproduction (reproductive tract). In performing these functions, the host is inevitably exposed to environmental antigens, food particles, commensal flora, and pathogens. Mucosal surfaces contain specialized dendritic cells (DCs) capable of sensing these external stimuli and mounting appropriate local responses depending on the nature of the elements they encounter. In the absence of pathogens, mucosal DCs either ignore the antigen or induce regulatory responses. Upon recognition of microorganisms that invade the mucosal barrier, mucosal DCs mount robust protective immunity. This review highlights progress in our understanding of how mucosal DCs process external information and direct appropriate responses by mobilizing various cells of the innate and adaptive immune systems to achieve homeostasis and protection.

Interaction of mature CD3+CD4+ T cells with dendritic cells triggers the development of tertiary lymphoid structures in the thyroid

Ectopic expression of CC chemokine ligand 21 (CCL21) in the thyroid leads to development of lymphoid structures that resemble those observed in Hashimoto thyroiditis. Deletion of the inhibitor of differentiation 2 (Id2) gene, essential for generation of CD3-CD4+ lymphoid tissue-inducer (LTi) cells and development of secondary lymphoid organs, did not affect formation of tertiary lymphoid structures. Rather, mature CD3+CD4+ T cells were critical for the development of tertiary lymphoid structures. The initial stages of this process involved interaction of CD3+CD4+ T cells with DCs, the appearance of peripheral-node addressin-positive (PNAd+) vessels, and production of chemokines that recruit lymphocytes and DCs. These findings indicate that the formation of tertiary lymphoid structures does not require Id2-dependent conventional LTis but depends on a program initiated by mature CD3+CD4+ T cells.

Comparative study of macrophage response in mice after DNA immunization and infection with herpes simplex virus type 1

Functional activity of macrophages and intensity of T cell immune response in mice were studied after intravaginal and intraperitoneal infection with herpes simplex virus type 1 and DNA vaccination in combination with adjuvant treatment (recombinant granulocyte-macrophage colony-stimulating factor and glucosaminylmuramyl dipeptide). DNA vaccination induced a virus-specific T cell immune response with no macrophagic inflammatory reaction. Infection with herpes simplex virus type 1 was accompanied by sustained inflammation, but not by the T cell immune response.

Restraint stress decreases virus-induced pro-inflammatory cytokine mRNA expression during acute Theiler's virus infection

Stressful life events have been associated with the onset and/or exacerbation of multiple sclerosis (MS). Our previous studies have indicated that restraint stress (RS) reduces inflammation and virus-induced chemokine expression in the Theiler's virus-induced demyelination (TVID) model of MS. Here we report that RS significantly reduced the virus-induced interferon-gamma mRNA levels in the brain. Additionally, mRNA levels of lymphotoxin-beta, tumor necrosis factor-alpha, and interferon-gamma in the brain were negatively correlated with viral titers in the brain. These results indicated an immunosuppressive effect of stress during early TVID causing impaired viral clearance, which may be a potential exacerbating factor for later demyelination.

Lymphoid organ development: from ontogeny to neogenesis

The development of lymphoid organs can be viewed as a continuum. At one end are the 'canonical' secondary lymphoid organs, including lymph nodes and spleen; at the other end are 'ectopic' or tertiary lymphoid organs, which are cellular accumulations arising during chronic inflammation by the process of lymphoid neogenesis. Secondary lymphoid organs are genetically 'preprogrammed' and 'prepatterned' during ontogeny, whereas tertiary lymphoid organs arise under environmental influences and are not restricted to specific developmental 'windows' or anatomic locations. Between these two boundaries are other types of lymphoid tissues that are less developmentally but more environmentally regulated, such as Peyer's patches, nasal-associated lymphoid tissue, bronchial-associated lymphoid tissue and inducible bronchial-associated lymphoid tissue. Their regulation, functions and potential effects are discussed here.

Lymphotoxin plays a crucial role in the development and function of nasal-associated lymphoid tissue through regulation of chemokines and peripheral node addressin

The mechanism of nasal-associated lymphoid tissue (NALT) development is incompletely understood with regard to the roles of cytokines, chemokines, and vascular addressins. Development of the wild-type NALT continued in the immediate postnatal period with gradual increases in cellularity, compartmentalization into T- and B-cell zones, and expression of lymphotoxin (LT)-alpha, LT-beta, and lymphoid chemokines (CCL21, CCL19, CXCL13). High endothelial venules (HEVs) developed that expressed GlyCAM-1, HEC-6ST [an enzyme crucial for expression of luminal peripheral node addressin (PNAd)], and PNAd itself. LT-beta(-/-) and LT-alpha(-/-) NALTs had fewer cells than those of wild-type mice, reduced (LT-beta(-/-)) or absent (LT-alpha(-/-)) lymphoid chemokines, and no T- and B-cell compartmentalization. LT-beta(-/-) HEVs expressed only abluminal PNAd and no HEC-6ST or GlyCAM-1. LT-alpha(-/-) HEVs had no PNAd, HEC-6ST, or GlyCAM-1. Because intranasal immunization gives rise to vaginal IgA, immunization of LT-beta(-/-) mice, which retain cervical lymph nodes, might generate such a response. Intranasal immunization with ovalbumin and cholera toxin revealed lower cytokine levels in the LT-alpha(-/-) and LT-beta(-/-) NALTs, and undetectable vaginal IgA. In contrast, splenic cytokines and serum IgG titers, although reduced, were detectable. These data indicate that LT-alpha(3) and LT-alpha(1)beta(2) cooperatively contribute to NALT development and function through regulation of lymphoid chemokines and adhesion molecules; they are the first to implicate LT-alpha(1)beta(2) in GlyCAM-1 regulation in NALT HEV development.