A replication-incompetent virus possessing an uncleavable hemagglutinin as an influenza vaccine

Vaccination is one of the most effective measures to protect against influenza virus infection. Inactivated and live-attenuated influenza vaccines are available; however, their efficacy is suboptimal. To develop a safe and more immunogenic vaccine, we produced a novel replication-incompetent influenza virus that possesses uncleavable hemagglutinin (HA) and tested its vaccine potential. The uncleavable HA was engineered by substituting the arginine at the C-terminus of HA1 with threonine, which prevents cleavage of HA into its HA1 and HA2 subunits, preventing fusion between the host and viral membranes. Although this fusion-deficient HA influenza virus that possesses uncleavable HA (uncleavable HA virus) could undergo multiple cycles of replication in only wild-type HA-expressing cells, it could infect normal cells and express viral proteins in infected cells, but could not generate infectious virus from infected cells due to the uncleavable HA. When C57BL/6 mice were intranasally immunized with the uncleavable HA virus, influenza-specific IgG and IgA antibodies were detected in nasal wash and bronchoalveolar lavage samples and in serum. In addition, influenza-specific CD8(+) T cells accumulated in the lungs of these mice. Moreover, mice immunized with the uncleavable HA virus were protected against a challenge of lethal doses of influenza virus, unlike mice immunized with a formalin-inactivated virus. These findings demonstrate that this fusion-deficient virus, which possesses uncleavable HA, is a suitable influenza vaccine candidate.

The innate immune response to cytomegalovirus: the kick-start (170.1)

Like all herpesviruses, cytomegalovirus (CMV, a β-herpesvirus) persists for the lifetime of its host. Primary infection is sub-clinical in healthy individuals, but can cause serious disease when immunity is compromised or naïve. We have previously shown the initial type I Interferon (IFNαβ) produced by the splenic stroma within hours after mouse CMV (MCMV) infection is dependent on lymphotoxin (LT)-LTβR signaling. We now show it is splenic marginal zone (MZ) stromal cells that are initially infected by MCMV and produce this initial IFNαβ. This “first wave” of IFNαβ is critical to restrict MCMV production from the MZ stroma, inhibiting the earliest measurable viral burst by 100-1000 fold. NK cells are key controllers of MCMV in the first few days of infection, but their role in restricting this first burst of MCMV is unclear. Depleting NK cells revealed them to contribute to initial control of MCMV production from the MZ stroma. Additional studies revealed NK cells can mediate their earliest effector function(s) independently of both IFNαβ and Ly49H, a key NK activating receptor that binds the MCMV m157 protein. Strikingly, the levels of MCMV produced from MZ stroma at the earliest time measurable are the highest observed at any subsequent time point prior to immune control of MCMV. These results highlight the importance of both IFNαβ and NK cells in controlling initial MCMV replication and spread, establishing a baseline for MCMV production over the course of acute infection.

Implications of nasopharynx-associated lymphoid tissue (NALT) in the development of allergic responses in an allergic rhinitis mouse model

BACKGROUND

Nasopharynx-associated lymphoid tissue (NALT) serves as an important inductive site for mucosal immunity in the upper respiratory tract. Despite its importance in the mucosal immune system, little is known regarding the role of NALT in airway allergic immune responses. We aimed to elucidate the role of NALT in the induction of upper airway allergic responses in a mouse model.

METHODS

Inhibitor of DNA binding/differentiation 2 (Id2)(-/-) and Id2(+/-) mice was exposed to the ovalbumin (OVA)-induced allergic rhinitis model, because the former resulted in the NALT deficiency. The allergic parameters, such as allergic symptoms, serum OVA-specific immunoglobulin E (IgE) levels, eosinophil infiltration, and cytokine profiles in the nasal mucosa, were compared between Id2(-/-) and Id2(+/-) groups.

RESULTS

NALT-null, Id2(-/-) mice displayed significantly lower allergic responses compared with Id2(+/-) mice, as demonstrated by lower levels of allergic symptoms, serum OVA-specific IgE, eosinophilic infiltration, and local Th2 cytokine transcriptions. To determine which of two factors, that is, the absence of NALT or the alteration of immunocompetent cell populations caused by the Id2 deficiency, has a larger effect on the attenuated allergic immune responses in Id2(-/-) mice, lethally irradiated Id2(-/-) mice were engrafted with C57BL/6 wild-type bone marrow cells and showed still significantly lower allergic immune responses compared with equally treated Id2(+/-) mice. In addition, IgE class switch recombination-associated molecules, such as ε immunoglobulin heavy-chain germline gene transcript, ε mRNA, and activation-induced cytidine deaminase mRNA, were detected in NALT from OVA-sensitized wild-type mice.

CONCLUSION

These results show the critical role of NALT for the induction of allergic responses in the upper airway at least in part by means of class switching to IgE in situ.

Chronic stress modulates neural and cardiovascular responses during reversal learning

Animal studies have revealed that chronic stress shifts cognitive strategies from the flexible goal-directed action to the simple and rigid habit action. In addition, stress-induced atrophy in the prefrontal cortex and dorsomedial striatum which are involved in the goal-directed action and hypertrophy of the dorsolateral striatum which is critical for the habit action were parallel with the effects of chronic stress on behaviors. The present study tested whether these previous findings in animal studies are compatible in humans by analyzing effects of chronic stress on neural and cardiovascular responses, which are likely important for performing appropriate actions. Twenty healthy men exposed to low or high chronic job stress performed a stochastic reversal learning task, which required cognitive flexibility and the goal-directed action. Regional cerebral blood flow was evaluated during the task using (15)O-water positron emission tomography, and cardiovascular parameters such as blood pressure and heart rate were also measured. During the reversal learning task, whereas participants with low chronic job stress exhibited activity in the anterior caudate, as well as orbitofrontal cortex, ventrolateral prefrontal cortex, insula, and midbrain, which might be related to the goal-directed action, participants with high chronic job stress exhibited no activity in such brain regions. Furthermore, participants with high chronic job stress exhibited less reactivity in diastolic blood pressure, which might be mediated by anterior cingulate cortical activity. These findings, in line with previous studies, suggested that chronic job stress correlates with less activity in brain regions related to the goal-directed action, and insensitive physiological responses in humans.

Nitric oxide modulates TGF-beta-directive signals to suppress Foxp3+ regulatory T cell differentiation and potentiate Th1 development

TGF-β can induce Foxp3(+) inducible regulatory T cells (Treg) and also synergize with IL-6 and IL-4 to induce Th17 and Th9 cells. We now report that NO modulates TGF-β activity away from Treg but toward the Th1 lineage. NO potentiated Th1 differentiation in the presence of TGF-β in both IL-12-independent and -dependent fashions by augmenting IFN-γ-activated STAT-1 and T-bet. Differentiation into Treg, Th1, and Th17 lineages could be modulated by NO competing with other cofactors, such as IL-6 and retinoic acid. NO antagonized IL-6 to block TGF-β-directed Th17 differentiation, and together with IL-6, NO suppressed Treg development induced by TGF-β and retinoic acid. Furthermore, we show that physiologically produced NO from TNF and inducible NO synthase-producing dendritic cells can contribute to Th1 development predominating over Treg development through a synergistic activity induced when these cells cocluster with conventional dendritic cells presenting Ag to naive Th cells. This illustrates that NO is another cofactor allowing TGF-β to participate in development of multiple Th lineages and suggests a new mechanism by which NO, which is associated with protection against intracellular pathogens, might maintain effective Th1 immunity.

The airway antigen sampling system: respiratory M cells as an alternative gateway for inhaled antigens

In this study, we demonstrated a new airway Ag sampling site by analyzing tissue sections of the murine nasal passages. We revealed the presence of respiratory M cells, which had the ability to take up OVA and recombinant Salmonella typhimurium expressing GFP, in the turbinates covered with single-layer epithelium. These M cells were also capable of taking up respiratory pathogen group A Streptococcus after nasal challenge. Inhibitor of DNA binding/differentiation 2 (Id2)-deficient mice, which are deficient in lymphoid tissues, including nasopharynx-associated lymphoid tissue, had a similar frequency of M cell clusters in their nasal epithelia to that of their littermates, Id2(+/-) mice. The titers of Ag-specific Abs were as high in Id2(-/-) mice as in Id2(+/-) mice after nasal immunization with recombinant Salmonella-ToxC or group A Streptococcus, indicating that respiratory M cells were capable of sampling inhaled bacterial Ag to initiate an Ag-specific immune response. Taken together, these findings suggest that respiratory M cells act as a nasopharynx-associated lymphoid tissue-independent alternative gateway for Ag sampling and subsequent induction of Ag-specific immune responses in the upper respiratory tract.

Low Temperature Synthesis of Plasma Teos SiO2

In this study, we investigated the deposition temperature's affect on TEOS based Si02 properties and reaction mechanisms while changing the excitation frequency. We used a parallel-plate plasma reactor, and either 100 kHz or 13.56 MHz radio frequency to generate plasma. We found that 100 kHz plasma promotes SiO formation and improves the film properties at low deposition temperatures. We assume this to be due to the supplement of higher energy ions to the substrate surface in 100 kHz plasma. This in turn promotes the elimination reaction (condensation reaction) of OH that links to Si atoms as a terminator of surface SiO networks or precursor molecules.

HVEM-LIGHT interactions promote generation of memory Th2 cells that mediate lung inflammation (91.8)

Memory Th2 cells are important in the pathogenesis of allergic responses including asthma, orchestrating recruitment of eosinophils and other inflammatory cells. Members of the tumor necrosis factor (TNF) receptor superfamily have emerged as key contributors to T cell activity, and therefore we investigated whether the engagement of the herpesvirus entry mediator (HVEM) on T cells by the TNF family molecule LIGHT controls Th2 mediated lung inflammation. Using systems where either HVEM or LIGHT are only defective on responding antigen-specific T cells, we demonstrated that the presence of HVEM on T cells is indispensible for the generation and persistence of Th2 memory cells and for allergen-induced Th2 lung inflammation, despite having a limited effect on early Th2 effector responses. Using adoptive co-transfer experiments we demonstrate that HVEM-LIGHT interaction on CD4 T cells can support longevity of T cells and promote memory generation. We also observed reduced activity of protein kinase B (PKB/Akt) and NF-κB in HVEM-deficient effector CD4 T cells, correlating with their poor survival. Furthermore, expression of an active form of PKB in HVEM-deficient T cells rescued Th2 cell survival in vivo, and restored lung inflammation in recall responses. Collectively, our results demonstrate a critical role of HVEM signals in the pathogenesis of Th2 derived lung inflammation and suggest that blocking of HVEM-LIGHT interactions could be a novel therapeutic target for asthma

[A case of secondary pulmonary alveolar proteinosis associated with myelodysplastic syndrome, complicated with disseminated M. abscessus infection]

A 27-year-old man was admitted to our hospital complaining of a persistent high fever since August 2007. Chest radiography showed infiltration shadows in the right lower lung field. Chest CT revealed scattered small nodular shadows and patchy consolidations in the right lower lobe. He was diagnosed as secondary pulmonary alveolar proteinosis (sPAP) associated with myelodysplastic syndrome (MDS), confirmed by video-assisted thoracic surgery (VATS) and bone marrow aspiration. Sera were negative for anti-granulocyte-macrophage colony-stimulating factor (GM-CSF) autoantibody. He developed a subcutaneous abscess and meningitis caused by M. absessus after VATS. After a long-course of antibiotic therapy, an allogenic peripheral blood stem cell transplantation was performed. But he died of graft versus host disease and M. abscessus sepsis 87 days after transplantation.

T cell intrinsic heterodimeric complexes between HVEM and BTLA determine receptivity to the surrounding microenvironment

The inhibitory cosignaling pathway formed between the TNF receptor herpesvirus entry mediator (HVEM, TNFRSF14) and the Ig superfamily members, B and T lymphocyte attenuator (BTLA) and CD160, limits the activation of T cells. However, BTLA and CD160 can also serve as activating ligands for HVEM when presented in trans by adjacent cells, thus forming a bidirectional signaling pathway. BTLA and CD160 can directly activate the HVEM-dependent NF-kappaB RelA transcriptional complex raising the question of how NF-kappaB activation is repressed in naive T cells. In this study, we show BTLA interacts with HVEM in cis, forming a heterodimeric complex in naive T cells that inhibits HVEM-dependent NF-kappaB activation. The cis-interaction between HVEM and BTLA is the predominant form expressed on the surface of naive human and mouse T cells. The BTLA ectodomain acts as a competitive inhibitor blocking BTLA and CD160 from binding in trans to HVEM and initiating NF-kappaB activation. The TNF-related ligand, LIGHT (homologous to lymphotoxins, exhibits inducible expression, and competes with HSV glycoprotein D for HVEM, a receptor expressed by T lymphocytes, or TNFSF14) binds HVEM in the cis-complex, but NF-kappaB activation was attenuated, suggesting BTLA prevents oligomerization of HVEM in the cis-complex. Genetic deletion of BTLA or pharmacologic disruption of the HVEM-BTLA cis-complex in T cells promoted HVEM activation in trans. Interestingly, herpes simplex virus envelope glycoprotein D formed a cis-complex with HVEM, yet surprisingly, promoted the activation NF-kappaB RelA. We suggest that the HVEM-BTLA cis-complex competitively inhibits HVEM activation by ligands expressed in the surrounding microenvironment, thus helping maintain T cells in the naive state.

Id2-, RORgammat-, and LTbetaR-independent initiation of lymphoid organogenesis in ocular immunity

The eye is protected by the ocular immunosurveillance system. We show that tear duct–associated lymphoid tissue (TALT) is located in the mouse lacrimal sac and shares immunological characteristics with mucosa-associated lymphoid tissues (MALTs), including the presence of M cells and immunocompetent cells for antigen uptake and subsequent generation of mucosal immune responses against ocularly encountered antigens and bacteria such as Pseudomonas aeruginosa. Initiation of TALT genesis began postnatally; it occurred even in germ-free conditions and was independent of signaling through organogenesis regulators, including inhibitor of DNA binding/differentiation 2, retinoic acid–related orphan receptor γt, lymphotoxin (LT) α1β2–LTβR, and lymphoid chemokines (CCL19, CCL21, and CXCL13). Thus, TALT shares immunological features with MALT but has a distinct tissue genesis mechanism and plays a key role in ocular immunity.

LKB1 mutations in mucinous bronchioloalveolar carcinoma occurring in Peutz-Jeghers syndrome patients

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Background: Mutations in the gene encoding Liver Kinase B1, LKB1, are common in patients with Peutz-Jeghers syndrome (PJS), which is characterized by mucocutaneous pigmentation, intestinal polyps and a high incidence of cancers at variable sites (colorectal, gynecological, breast, pancreas, and lung). Although tumors occurring in PJS patients are known to contain mucin-rich conmponents, mucinous bronchioloalveolar carcinomas (mBACs) arising from the PJS background have only rarely been reported. Here we report two mBAC patients with PJS. We further explored the LKB1 gene in these two patients and, in addition, eight sporadic mBAC patients. Methods: Frozen tissue specimens were collected from ten mBAC patients who underwent surgery in our department from 2002 to 2008, and high molecular weight genomic DNA was extracted from them and stocked in the bio-bank. Written informed consent was obtained from each patient, and ethical approval was obtained from the IRB. The nucleotide sequence of LKB1 (EX01–09) was determined by genomic PCR-direct sequencing. Loss of heterozygosity (LOH) was analyzed by high resolution fluorescent microsatellite analysis (HRFMA) using two microsatellite markers that encompass the LKB1 locus, D19S886 and D19S565. Results: Among 11 tumors derived from the 10 patients, 9 distinct LKB1 mutations were found in 7 tumors (4 G:C to A:T transitions; 3 G:C to C:G transversions; 2 single nucleotide insetion/deletion). All of three tumors obtained from the two PJS patients harbored a same sequence alteration. Although LOH was not observed in these tumors, independent sequence alterations were found in two of the three tumors, which may suggest biallelic inactivation of LKB1 in tumors occurred in the PJS patients. Conclusions: The relatively high frequency of LKB1 mutation in mBAC patients may suggest its implication in lung carcinogenesis, at least in mBAC, and its potential as a therapeutic target.

[Table: see text]

No significant financial relationships to disclose.

Apparatus for material tests using an internal loading system in high-pressure gas at room temperature

A new type of apparatus for material tests using an internal loading system in high-pressure gas up to 100 MPa at room temperature without conventional material testing equipment was developed. The apparatus consists of a high-pressure control system and a pressure vessel, in which a piston is installed in the cylinder of the pressure vessel. The load caused by the pressure difference between spaces separated by the piston in the vessel cylinder is applied on the specimen connected to the piston in the vessel cylinder. The actual load on the specimen is directly measured by an external load cell and the displacement of the specimen is also measured by an external extensometer. As an example of the application of the apparatus, a tensile test on SUS316 stainless steel the Japanese Industrial Standard (JIS) G4303, which is comparable to the type 316 stainless steel ASTM A276, was conducted in 90 MPa hydrogen and argon. Hydrogen showed a marked effect on the tensile property of the material. The hydrogen gas embrittlement of the material was briefly discussed.

Regulatory role of lymphoid chemokine CCL19 and CCL21 in the control of allergic rhinitis

The lymphoid chemokines CCL19 and CCL21 are known to be crucial both for lymphoid cell trafficking and for the structural organization of lymphoid tissues such as nasopharynx-associated lymphoid tissue (NALT). However, their role in allergic responses remains unclear, and so our current study aims to shed light on the role of CCL19/CCL21 in the development of allergic rhinitis. After nasal challenge with OVA, OVA-sensitized plt (paucity of lymph node T cells) mice, which are deficient in CCL19/CCL21, showed more severe allergic symptoms than did identically treated wild-type mice. OVA-specific IgE production, eosinophil infiltration, and Th2 responses were enhanced in the upper airway of plt mice. Moreover, in plt mice, the number of CD4(+)CD25(+) regulatory T cells declined in the secondary lymphoid tissues, whereas the number of Th2-inducer-type CD8alpha(-)CD11b(+) myeloid dendritic cells (m-DCs) increased in cervical lymph nodes and NALT. Nasal administration of the plasmid-encoding DNA of CCL19 resulted in the reduction of m-DCs in the secondary lymphoid tissues and the suppression of allergic responses in plt mice. These results suggest that CCL19/CCL21 act as regulatory chemokines for the control of airway allergic disease and so may offer a new strategy for the control of allergic disease.

A novel M cell-specific carbohydrate-targeted mucosal vaccine effectively induces antigen-specific immune responses

Mucosally ingested and inhaled antigens are taken up by membranous or microfold cells (M cells) in the follicle-associated epithelium of Peyer's patches or nasopharynx-associated lymphoid tissue. We established a novel M cell–specific monoclonal antibody (mAb NKM 16–2-4) as a carrier for M cell–targeted mucosal vaccine. mAb NKM 16–2-4 also reacted with the recently discovered villous M cells, but not with epithelial cells or goblet cells. Oral administration of tetanus toxoid (TT)– or botulinum toxoid (BT)–conjugated NKM 16–2-4, together with the mucosal adjuvant cholera toxin, induced high-level, antigen-specific serum immunoglobulin (Ig) G and mucosal IgA responses. In addition, an oral vaccine formulation of BT-conjugated NKM 16–2-4 induced protective immunity against lethal challenge with botulinum toxin. An epitope analysis of NKM 16–2-4 revealed specificity to an α(1,2)-fucose–containing carbohydrate moiety, and reactivity was enhanced under sialic acid–lacking conditions. This suggests that NKM 16–2-4 distinguishes α(1,2)-fucosylated M cells from goblet cells containing abundant sialic acids neighboring the α(1,2) fucose moiety and from non-α(1,2)-fucosylated epithelial cells. The use of NKM 16–2-4 to target vaccine antigens to the M cell–specific carbohydrate moiety is a new strategy for developing highly effective mucosal vaccines.

Neuroregulator RET initiates Peyer's-patch tissue genesis

The tyrosine kinase receptor RET regulates the intestinal nervous system. A recent paper by Veiga-Fernandes et al. (2007) demonstrates that RET is also involved in the intestinal immune system through the initiation of Peyer's-patch tissue genesis.

Presence of Id2− and RORγt-independent lymphoid tissue organogenesis (81.2)

Id2 and RORγt have been shown to be the essential transcriptional regulators for the differentiation of CD3−CD4+CD45+ lymphoid tissue inducer cells (LTi). LTi migrate to the site of tissue genesis and provide the signal mediated by membrane-bound lymphotoxin (LT)α1β2, which results in the subsequent production of chemokines and adhesion molecules including CXCL13 and VCAM-1 by LTβR+ stromal cells. Organogenesis of lymphoid tissues such as Peyer’s patches are thus defective in Id2−/−, RORγt−/− and LTα−/− mice. Tear duct-associated lymphoid tissue (TALT) has been identified in human. However, the molecular and cellular requirements of TALT-genesis are totally unknown. Here we provide the first definitive evidence for the presence of Id2− and RORγt-independent tissue genesis program. We thus located the murine TALT in nasolacrimal duct and revealed that TALT-genesis did not require Id2, RORγt and LTα. TALT-genesis was initiated at postnatal days and developed in germ free and MyD88−/− mice. These results demonstrated that TALT has indeed developed using the unique pathway compared with other secondary lymphoid organs.

Different profiles of IL-10+IFN-gamma-IL-4-CD4+ T cells in the peripheral blood in atopic and non-atopic asthmatics

BACKGROUND

The impaired production of interleukin (IL) 10 from regulatory T cells has been proposed as a causal mechanism of asthma. Although IL-10-producing (IL-10+) T cells are detectable in the peripheral blood, their significance in the pathophysiology of asthma remains uncertain.

OBJECTIVES

This study aimed to investigate the profile of circulating IL-10+CD4+ T cells in atopic and non-atopic asthma.

METHODS

Atopic and non-atopic asthmatics were divided into a mild and severe group. Their peripheral blood mononuclear cells (PBMCs) were stimulated with anti-CD3 and anti-CD28 antibodies and then processed for triple cytokine flow cytometry directed to IL-10, interferon (IFN) gamma and IL-4.

RESULTS

IL-10+CD4+ cells were exclusively detected in the IFN-gamma-IL-4- population. In atopic asthma, the frequency of IL-10+IFN-gamma-IL-4-CD4+ cells in the severe group was significantly lower than that in the mild group. The frequency of IL-10+IFN-gamma-IL-4-CD4+ cells in the severe group was not significantly different from that in the mild group of those with non-atopic asthma. The frequency of IL-4+IFN-gamma-IL-10-CD4+ cells (Th2) was significantly higher in the group with mild atopic asthma than in that with mild non-atopic asthma. IFN-gamma+IL-4-IL-10-CD4+ cells (Th1) did not differ between groups, irrespective whether the subjects suffered from atopic or non-atopic asthma.

CONCLUSIONS

IL-10+CD4+ cells in PBMCs may be distinct from Th1 or Th2 and likely have the profile of regulatory T cells. The differential association of IL-10+IFN-gamma-IL-4-CD4+ cells with clinical severity between atopic and non-atopic asthma implies that its pathophysiological significance may differ among asthma phenotypes.

Intranasal immunization with phosphorylcholine induces antigen specific mucosal and systemic immune responses in mice

Phosphorylcholine (PC) is a structural component of a wide variety of pathogens including Streptococcus pneumoniae and Haemophilus influenzae, and anti-PC immune responses are known to protect mice against invasive bacterial diseases. The present study tested the capability of PC as an intranasal plurispecific vaccine against upper airway infections. BALB/c mice immunized with intranasal PC-keyhole limpet hemocyanin (KLH) plus cholera toxin (CT) as a mucosal adjuvant showed increased PC-specific IgM in serum, IgA in nasal wash and saliva, and numbers of PC-specific nasal and splenic antibody producing cells. Enhanced production of IL-4 and IFN-gamma by CD4+ T cells indicated the participation of Th2- and Th1-type cells. Salivary IgA antibodies produced by intranasal immunization with PC-KLH plus CT reacted to most strains of S. pneumoniae and H. influenzae. Further we demonstrated that the clearance of S. pneumoniae and H. influenzae from the nasal tract was significantly enhanced by nasal immunization with PC-KLH and CT. Thus, intranasal vaccination to induce PC-specific immune responses might help to prevent upper airway infections caused by S. pneumoniae and H. influenzae.

Cutting edge: Uniqueness of lymphoid chemokine requirement for the initiation and maturation of nasopharynx-associated lymphoid tissue organogenesis

CD3(-)CD4(+)CD45(+) inducer cells are required for the initiation of mucosa-associated organogenesis of both nasopharynx-associated lymphoid tissues (NALT) and Peyer's patches (PP) in the aerodigestive tract. CXCL13(-/-) mice and mice carrying the paucity of lymph node T cell (plt) mutation and lacking expression of CCL19 and CCL21 accumulate CD3(-)CD4(+)CD45(+) cells at the site of NALT but not of PP genesis. Although NALT was observed to develop in adult CXCL13(-/-) and plt/plt mice, the formation of germinal centers in CXCL13(-/-) mice was affected, and their population of B cells was much lower than in the NALT of CXCL13(+/-) mice. Similarly, fewer T cells were observed in the NALT of plt/plt mice than in control mice. These findings indicate that the initiation of NALT organogenesis is independent of CXCL13, CCL19, and CCL21. However, the expression of these lymphoid chemokines is essential for the maturation of NALT microarchitecture.