Abstract
purpose. To investigate the role macrophages play in controlling herpes simplex
virus (HSV)-1 replication after infection of the murine cornea.
methods. Macrophage depletion in selected tissues before or after virus
infection was achieved by repeated subconjunctival (SCJ) and/or
intravenous (IV) injection of liposomes containing dichloromethylene
diphosphonate (L-Cl2MDP). Controls received liposomes
containing phosphate-buffered saline (L-PBS). The efficiency of
depletion was evaluated by histologic examination. Virus content in
infected tissues was determined by standard plaque assay. Delayed-type
hypersensitivity (DTH) responsiveness was assessed using the
ear-swelling assay. Antibody isotype responses to virus antigens and
cytokine production were monitored by enzyme-linked immunosorbent
assay.
results. Balb/c mice given SCJ injection of L-Cl2MDP 4 and 2 days
before HSV-1 corneal infection were found to have ocular virus titers
as much as 105-fold higher than that seen in the
L-PBS–treated controls 8 days after infection. When
L-Cl2MDP treatment was delayed until 2 and 4 days after
infection, virus titers in the eye were analogous to those in the
control animals. Subconjunctival and submandibular lymph node
macrophages in mice given local (SCJ) L-Cl2MDP pretreatment
were profoundly reduced, whereas the number of corneal Langerhans’
cells and lymph node dendritic cells remained unchanged. Local
L-Cl2MDP pretreatment was associated with significantly
reduced DTH responsiveness to HSV-1 antigen, and an alteration in
selected antibody isotype production. Depletion of macrophages in the
subconjunctival tissue before corneal infection was not accompanied by
enhanced virus growth at early times (2 or 4 days) after infection.
conclusions. Macrophages play an important role in restricting HSV-1 growth after
corneal infection. These cells appear to be required for the
development of an acquired immune response, presumably by functioning
in antigen processing and presentation. The hypothesis that macrophages
are major participants in innate immunity to HSV-1 corneal infection
was not supported.
Herpes simplex virus (HSV)-1 infection on the scarified murine
cornea results in virus replication in ocular tissue and in the
trigeminal ganglion. At a high infectious dose, the virus may spread to
the brain and cause fatal encephalitis. After a moderate challenge dose
in immunocompetent Balb/c mice, the virus is usually eliminated by days
7 through 9 in the cornea
1 and by days 9 through 12 in the
trigeminal ganglion (Cheng and Lausch, unpublished
observations, May 1997). Studies have shown that interferon
(IFN)-α/β and neutrophils, components of the innate immune
response, play a critical role in containing HSV-1 growth. Thus, in
mice treated with neutralizing antibody to IFN-α/β or without the
IFN-α/β receptor, virus titers were substantially elevated, and
corneal opacity scores were increased.
2 3 4 Depletion of
neutrophils was associated with elevated virus titers in the eye 3 days
after infection, and fatal encephalitis subsequently developed in the
majority of animals.
1
Although innate immunity is important, an acquired immune response is
usually needed to terminate HSV-1 replication. Consequently, humans and
animals with impaired T-cell–mediated immunity can experience severe
and even life-threatening infections.
1 5 In the mouse, the
CD4
+ T cell subset is dominant in effecting
cessation of virus growth after ocular infection.
6 Antibodies can also help to suppress HSV-1 replication in the eye of
immunized hosts
7 and can suppress the immunopathologic
response to ocular infection.
8 9 Macrophages have been
reported to be active participants in host resistance to HSV-1
infection.
10 11 Two general types of macrophage-mediated
resistance mechanisms have been described.
12 One is called
intrinsic resistance and refers to the capacity of the macrophage to
inhibit virus growth within itself. The second is called extrinsic
resistance and relates to the macrophage’s ability to inactivate
extracellular virus, suppress virus replication in adjacent cells, and
destroy infected cells. Activated macrophages can produce and release
antiviral factors such as IFN-α/β and tumor necrosis factor
(TNF)-α. The latter has been shown on passive transfer to protect
mice from intraperitoneal infection.
13 TNF-α also can
synergize with IFN-γ to induce IFN-β, which in turn suppresses
HSV-1 growth in cultured human corneal fibroblasts and epithelial
cells.
14 15 Macrophages also have the potential to produce
chemokines, which can recruit and activate additional cell types to
combat virus infection.
16 In addition to contributing to
innate immunity, macrophages are able to process and present antigen to
T lymphocytes. After phagocytosis of particulate antigen, B7 and major
histocompatibility complex class II molecules are expressed that serve
as costimulatory signals to activate naive T cells.
17 18 19
Macrophages can be selectively depleted through administration of
liposomes containing dichloromethylene diphosphonate
(L-Cl
2MDP). Treatment with this agent has been
shown to be selective, because only macrophages take up the
liposomes.
20 21 22 23 Release of the drug from the liposomes
leads to macrophage apoptosis by an unknown
mechanism.
24 25 After their elimination repopulation of
macrophages is highly variable, ranging from 1 week to 5 months
depending on the site of depletion.
21
It is presently unclear what role macrophages play in suppressing HSV-1
replication after corneal infection. To investigate this question,
Balb/c mice were treated with L-Cl2MDP before
infection. Studies were then conducted to assess what effect macrophage
depletion had on the expression of innate and acquired immunity.
DTH responsiveness in HSV-1 ocular-infected mice was determined
using the ear-swelling assay. The test antigen, HSV-1 RE, was diluted
in serum-free RPMI 1640 medium. The virus preparation was then exposed
to UV irradiation for 10 minutes. This reduced infectivity from
106 to less than 102 PFU/10μ
l. To test for DTH responsiveness, 10 μl of UV-irradiated virus
antigen was inoculated into the dorsal side of the mouse’s right ear 7
days after infection using a 50-μl syringe (Hamilton, Reno, NV) and a
30-gauge needle. The left ear (control) received 10 μl RPMI 1640 with
1% newborn calf serum. Ear swelling was measured 24 hours later in a
blind fashion using a micrometer (model 7326; Mitutoyo, Paramus, NJ).
The results are expressed as ear swelling of the right
(antigen-treated) ear minus ear swelling of the left (control-treated)
ear in units of 10−4 in.
To test the effect of L-Cl2MDP treatment on
HSV-1 replication in Balb/c mice, individual whole eyes and
subconjunctival tissues were excised. The collection of subconjunctival
tissue was guided by the following procedure. After enucleation, the
eyeball was cut sagittally and was then spread flat in a petri dish.
The cornea and retina were detached from the eye under a dissecting
microscope. The remaining part was the subconjunctiva. The individually
collected tissues were placed in 0.6 ml of 2% fetal bovine serum in
RPMI 1640 medium with 1% antibiotics. Preparations were frozen to−
70°C and then thawed and homogenized (Ten Broeck homogenizer;
Bellco, Vineland, NJ). The homogenates were frozen and thawed again,
followed by sonication for 30 seconds using a dismembrator (Sonic 300;
Artek Systems, Farmingdale, NY). The clarified supernatants were then
titrated for infectious virus content on Vero cell monolayers.
In the present study we investigated what effect depletion of
macrophages would have on ocular growth after HSV-1 corneal infection.
L-Cl2MDP given in SCJ injection before infection
was shown to deplete macrophages at the inoculation site and in the
regional lymph node. This treatment resulted in virus titers in the eye
8 days after infection that were strikingly enhanced (>5 log) compared
with L-PBS–treated controls. In marked contrast, virus replication was
not enhanced when L-Cl2MDP was administered
solely by the IV route before infection or when given by SCJ injection
plus IV 2 and 4 days after infection. Collectively, these results
suggest that macrophage participation is critical during the first 2
days after infection, and that macrophages residing in the bulbar
conjunctiva and/or draining lymph nodes are the functionally active
cells.
The requirement for local macrophages that are active during the first
48 hours after infection suggests that they may serve as accessory
cells for generating an acquired immune response. Alternatively, they
may contribute to innate resistance. Studies have shown that HSV-1
infection in the naive mouse is largely controlled by cell-mediated
immunity. Thus, if macrophages are involved in antigen presentation,
then it could be predicted that the cell-mediated immune response would
be depressed in hosts depleted of these cells. Indeed, we found that
DTH response was substantially reduced in animals given SCJ injection
of L-Cl
2MDP before infection. However, no
significant suppression was seen when the reagent was given IV before
or by SCJ injection plus IV after infection. Our results are
reminiscent of those reported by Karupiah et al.
40 They
found that elimination of macrophages through IV plus subcutaneous
L-Cl
2MDP treatment 4 and 2 days before
subcutaneously introduced infection impaired T-cell–mediated immunity
and enhanced ectromelia virus growth.
Depletion of macrophages before HSV-1 ocular infection also altered the
nature of the humoral immune response. Specifically, the antiviral IgM
titer was substantially increased, whereas the IgG2a titer was more
modestly elevated. One possible explanation for the elevated IgM titer
in our model is that in the absence of macrophages, virus particles
efficiently interact with B-cell immunoglobulin receptors, promoting
cross-linking and directly facilitating B-cell
activation.
41 Alternatively, or in addition, the humoral
immune response may be heightened because of the increased viral
antigen load seen in macrophage-depleted mice. Wijburg et
al.
42 depleted macrophages by IV administration of
L-Cl
2MDP before hepatitis virus infection. They
found that this treatment was also associated with heightened virus
titers and increased production of mainly IgG2a anti-hepatitis virus
antibody. In their study IgM antibody levels were not examined. The
cytotoxic T-lymphocyte response was not enhanced.
Although the IgM and IgG2a antibody isotypes were elevated, HSV-1
replication was not inhibited in the macrophage-depleted mice. One
explanation for this is that the large IgM antibody molecules may
diffuse very poorly from vascular into peripheral tissues. In addition,
we have observed that passive transfer of high-titer IgG2a neutralizing
antibody 24 hours after HSV-1 corneal infection does not accelerate
virus clearance from the eye.
8 Presumably, this is due at
least in part to the ability of HSV-1 to spread from cell to contiguous
cell without becoming exposed to extracellular antibody.
43 Thus, it is not surprising that the enhanced production of anti-HSV-1
IgM and IgG2a antibodies in the L-Cl
2MDP–treated
hosts was not associated with suppression of virus replication.
Zisman et al.
11 observed that animals depleted of
macrophages and then infected intraperitoneally with HSV-1 had an
increased viral load early after virus infection. Similar observations
have been made in macrophage-depleted mice infected with hepatitis
virus,
42 yellow fever virus,
44 or West Nile
virus.
45 Thus, we anticipated that macrophages contribute
to innate immunity and that L-Cl
2MDP given by SCJ
injection would result in elevated ocular HSV-1 titers at early time
points after infection. However, the virus titers at days 2 and 4 after
infection were similar to those seen in the L-PBS control animals.
Certain cytokines such as TNF-α have been shown to play a critical
role in promoting macrophage nonspecific anti-herpes
activity.
46 47 We, therefore, measured the levels of
TNF-α in the ocular tissue of mice infected for 2 and 4 days. Only
small amounts of TNF-α (approximately 40 pg/eye) were detected by
ELISA, and local L-Cl
2MDP pretreatment did not
reduce the level of TNF-α (data not shown). Thus, we could find no
evidence for macrophage-mediated nonspecific inhibition of virus
replication. Previous studies in our laboratory have shown that
neutrophil depletion was correlated with enhanced virus growth on day 3
after infection.
1 Taken together, our studies suggest that
in the anterior portion of the eye, neutrophils rather that macrophages
may be the dominant mediators of innate resistance.
Langerhans’ cells are normally found in the subconjunctival limbal
region of the cornea.
48 49 Studies in skin, where they are
abundant, have shown that these cells can capture antigen and then
migrate to the local lymph node where they can evolve into mature
dendritic cells with highly efficient antigen-presenting
capability.
34 35 36 37 We found that local
L-Cl
2MDP pretreatment did not deplete ocular
Langerhans’ cells. Additionally, the reagent did not deplete dendritic
cells, which is in accord with the reports of others.
21 50 Because Langerhans’ and dendritic cells can serve as
antigen-presenting cells in the generation of cell-mediated immunity,
it is surprising that they did not substitute for macrophages. There
are at least two possible explanations for these results. First, it may
be that macrophages are needed to transfer processed antigen to
Langerhans’ and dendritic cells.
50 Alternatively,
macrophages may secrete cytokines that facilitate dendritic cell
maturation into efficient antigen-presenting cells.
36 51
In summary, our studies demonstrate that macrophages play a critical
role in host resistance to HSV-1 ocular infection. Their function
appears to be one of involvement in antigen processing and
presentation. The failure to demonstrate a role for these cells in
innate immunity to HSV-1 infection may reflect their relatively low
numbers in the anterior segment of the eye.
Supported by Grant EY1143 from the National Institutes of Health, and the Lions/USA Eye Research Foundation.
Submitted for publication June 29, 1999; revised October 22, 1999; accepted November 30, 1999.
Commercial relationships policy: N.
Corresponding author: Robert N. Lausch, Department of Microbiology and Immunology, University of South Alabama, MSB 2096, Mobile, AL 36688.
[email protected]
Table 1. Effect of Local L-Cl2MDP Pretreatment on the Production of
Anti-HSV-1 Antibodies
Table 1. Effect of Local L-Cl2MDP Pretreatment on the Production of
Anti-HSV-1 Antibodies
Anti-HSV Ig Isotype* | Anti-HSV-1 Titer (×/÷SD), † | | P , ‡ |
| L-PBS | L-Cl2MDP | |
IgG1 | 5.5× 103 (×/÷2.6) | 2.8× 103 (×/÷1.7) | >0.05 |
IgG2a | 3.2× 104 (×/÷1.5) | 8.8× 104 (×/÷2.2) | <0.05 |
IgG2b | 1.6× 104 (×/÷2.0) | 2.2× 104 (×/÷1.7) | >0.05 |
IgG3 | 6.7× 103 (×/÷1.7) | 1.2× 104 (×/÷1.7) | >0.05 |
IgM | 8.4× 102 (×/÷1.9) | 3.6× 104 (×/÷1.9) | <0.01 |
Tumpey TM, Chen S-H, Oakes JE, Lausch RN. Neutrophil-mediated suppression of virus replication after herpes simplex virus type 1 infection of the murine cornea. J Virol
. 1996;70:898–904.
[PubMed]Su Y-H, Oakes JE, Lausch RN. Ocular avirulence of a herpes simplex virus type 1 strain is associated with heightened sensitivity of α/β interferon. J Virol
. 1990;64:2187–2192.
[PubMed]Hendricks RL, Weber PC, Taylor JL, Koumbis A, Tumpey TM, Glorioso JC. Endogenously produced interferon α protects mice from herpes simplex virus type 1 corneal disease. J Gen Virol
. 1991;72:1601–1610.
[CrossRef] [PubMed]Leib DA, Harrison TE, Laslo KM, Machalek MA, Moorman NJ, Virgin HW. Interferons regulate the phenotype of wild-type and mutant herpes simplex viruses in vivo. J Exp Med
. 1999;189:663–672.
[CrossRef] [PubMed]Rand KH, Rasmussen LE, Pollard R. B, Arvin A, Merigan TC. Cellular immunity and herpesvirus infections in cardiac-transplant patients. N Engl J Med
. 1977;296:1372–1377.
[CrossRef] [PubMed]Oakes JE, Rector JT, Lausch RN. Lyt-1
+ T cells participate in recovery from ocular herpes simplex virus type 1 infection. Invest Ophthalmol Vis Sci
. 1984;25:188–194.
[PubMed]Lausch RN, Monterio C, Kleinschrodt WR, Oakes JE. Superiority of antibody versus delayed hypersensitivity in clearance of HSV-2 from eye. Invest Ophthalmol Vis Sci
. 1987;28:565–570.
[PubMed]Lausch RN, Oakes JE, Metcalf JF, Scimeca JM, Smith LA, Robertson SM. Quantitation of purified monoclonal antibody needed to prevent HSV-1 induced stromal keratitis in mice. Curr Eye Res
. 1989;8:499–506.
[CrossRef] [PubMed]Staats H, Oakes JE, Lausch RN. Anti-glycoprotein D monoclonal antibody protects against herpes simplex virus type 1-induced diseases in mice functionally depleted of selected T-cell subsets or asialo GM1
+ cells. J Virol
. 1991;65:6008–6014.
[PubMed]Johnson RT. The pathogenesis of herpes virus encephalitis, II: a cellular basis for the development of resistance with age. J Exp Med
. 1964;120:359–374.
[CrossRef] [PubMed]Zisman B, Hirsch MS, Allison AC. Selective effects of anti-macrophage serum, silica, and anti-lymphocyte serum in pathogenesis of herpes virus infection of young adult mice. J Immunol
. 1970;104:1155–1159.
[PubMed]Wu L, Morahan PS. Macrophages and other non-specific defenses: role of modulating resistance against herpes simplex virus. Curr Top Microbiol Immunol
. 1992;179:89–110.
[PubMed]Rossol–Voth R, Rossol S, Schutt KH, Corridori S, deCian W, Falke D. In vivo protective effect of tumor necrosis factor α against experimental infection with herpes simplex virus type 1. J Gen Virol
. 1991;72:143–147.
[CrossRef] [PubMed]Chen S-H, Oakes JE, Lausch RN. Synergistic anti-HSV effect of tumor necrosis factor alpha and interferon gamma in human corneal fibroblasts is associated with interferon beta induction. Antiviral Res
. 1993;22:15–29.
[CrossRef] [PubMed]Chen S-H, Oakes JE, Lausch RN. Synergistic anti-herpes effect of TNF-α and IFN-γ in human corneal epithelial cells compared with that in corneal fibroblasts. Antiviral Res
. 1994;25:201–213.
[CrossRef] [PubMed]Widmer U, Manogue KR, Cerami A, Sherry B. Genomic cloning and promoter analysis of macrophage inflammatory protein (MIP)-2, MIP-1 alpha, and MIP-1 beta, members of the chemokine superfamily of proinflammatory cytokines. J Immunol
. 1993;150:4996–5012.
[PubMed]Ziegler K, Unanue ER. Identification of a macrophage antigen-processing event required for I-region-restricted antigen presentation to T lymphocytes. J Immunol
. 1981;127:1869–1875.
[PubMed]Ziegler HK, Unanue ER. Decrease in macrophage antigen catabolism caused by ammonia and chloroquine is associated with inhibition of antigen presentation to T cells. Proc Natl Acad Sci USA
. 1982;79:175–178.
[CrossRef] [PubMed]Unanue ER, Allen PM. The basis for the immunoregulatory role of macrophages and other accessory cells. Science
. 1987;236:551–557.
[CrossRef] [PubMed]Claassen I, van Rooijen N, Claassen E. A new method for removal of mononuclear phagocytes from heterogeneous cell populations in vitro, using the liposome-mediated macrophage ‘suicide’ technique. J Immunol Methods
. 1990;134:153–161.
[CrossRef] [PubMed]Delemarre FG, Kors N, Kraal G, van Rooijen N. Repopulation of macrophages in popliteal lymph nodes of mice after liposome-mediated depletion. J Leukoc Biol
. 1990;47:251–257.
[PubMed]Qian Q, Jutila MA, van Rooijen N, Cutler JE. Elimination of mouse splenic macrophages correlates with increased susceptibility to experimental disseminated candidiasis. J Immunol
. 1994;152:5000–5008.
[PubMed]van Rooijen N, Sanders A. Liposome mediated depletion of macrophages: mechanism of action, preparation of liposomes and applications. J Immunol Methods
. 1994;174:83–93.
[CrossRef] [PubMed]Naito M, Nagai H, Kawano S, et al. Liposome-encapsulated dichloromethylene diphosphonate induces macrophage apoptosis in vivo and in vitro. J Leukoc Biol
. 1996;60:337–344.
[PubMed]van Rooijen N, Sanders A, van den Berg TK. Apoptosis of macrophages induced by liposome-mediated intracellular delivery of clodronate and propamidine. J Immunol Methods
. 1996;193:93–99.
[CrossRef] [PubMed]Lausch RN, Kleinschrodt WR, Monteiro C, Kayes SG, Oakes JE. Resolution of HSV corneal infection in the absence of delayed-type hypersensitivity. Invest Ophthalmol Vis Sci
. 1985;26:1509–1515.
[PubMed]Staats HF, Nichols WG, Palker TJ. Mucosal immunity to HSV-1: systemic and vaginal antibody responses after intranasal immunization with the HIV-1 C4/V3 peptide T1SP10 MN(A). J Immunol
. 1996;157:462–472.
[PubMed]Staats HF, Montgomery SP, Palker TJ. Intranasal immunization is superior to vaginal, gastric, or rectal immunization for the induction of systemic and mucosal anti-HIV antibody responses. AIDS Res Hum Retroviruses
. 1997;13:945–952.
[CrossRef] [PubMed]van Klink F, Taylor WM, Alizadeh H, Jager MJ, van Rooijen N, Niederkorn JY. The role of macrophages in acanthamoeba keratitis. Invest Ophthalmol Vis Sci
. 1996;37:1271–1281.
[PubMed]Kraal G, Breel M, Janse M, Bruin G. Langerhans’ cells, veiled cells, and interdigitating cells in the mouse recognized by a monoclonal antibody. J Exp Med
. 1986;163:981–997.
[CrossRef] [PubMed]van Rooijen N, van Nieuwmegen R. Elimination of phagocytic cells in the spleen after intravenous injection of liposome-encapsulated dichloromethylene diphosphonate: an enzyme-histochemical study. Cell Tissue Res
. 1984;238:355–358.
[CrossRef] [PubMed]van Rooijen N, Kors N, van de Ende M, Dijkstra CD. Depletion and repopulation of macrophages in spleen and liver of rat after intravenous treatment with liposome-encapsulated dichloromethylene diphosphonate. Cell Tissue Res
. 1990;260:215–222.
[CrossRef] [PubMed]Tilney NL. Patterns of lymphatic drainage in the adult laboratory rat. J Anat
. 1971;109:369–383.
[PubMed]Macatonia SE, Knight SC, Edwards AJ, Griffiths S, Fryer P. Localization of antigen on lymph node dendritic cells after exposure to the contact sensitizer fluorescein isothiocyanate: functional and morphological studies. J Exp Med
. 1987;166:1654–1667.
[CrossRef] [PubMed]Larsen CP, Steinman RM, Witmer–Pack M, Hankins DF, Morris PJ, Austyn JM. Migration and maturation of Langerhans cells in skin transplants and explants. J Exp Med
. 1990;172:1483–1493.
[CrossRef] [PubMed]Cumberbatch M, Kimber I. Tumour necrosis factor-alpha is required for accumulation of dendritic cells in draining lymph nodes and for optimal contact sensitization. Immunology
. 1995;84:31–35.
[PubMed]Austyn JM. Antigen uptake and presentation by dendritic leukocytes. Semin Immunol
. 1992;4:227–236.
[PubMed]Chesnut RW, Colon SM, Grey HM. Requirements for the processing of antigens by antigen-presenting B cells, I: Functional comparison of B cell tumors and macrophages. J Immunol
. 1982;129:2382–2388.
[PubMed]Grey HM, Colon SM, Chesnut RW. Requirements for the processing of antigen by antigen-presenting B cells, II: Biochemical comparison of the fate of antigen in B cell tumors and macrophages. J Immunol
. 1982;129:2389–2395.
[PubMed]Karupiah G, Buller RM, van Rooijen N, Duarte CJ, Chen J. Different roles for CD4+ and CD8+ T lymphocytes and macrophage subsets in the control of a generalized virus infection. J Virol
. 1996;70:8301–8309.
[PubMed]Bachmann MF, Zinkernagel RM, Oxenius A. Immune responses in the absence of costimulation: viruses know the trick. J Immunol
. 1998;161:5791–5794.
[PubMed]Wijburg OL, Heemskerk MH, Boog CJ, van Rooijen N. Role of spleen macrophages in innate and acquired immune responses against mouse hepatitis virus strain A59. Immunology
. 1997;92:252–258.
[CrossRef] [PubMed]Lodmell DL, Niwa A, Hayashi K, Notkins AL. Prevention of cell-to-cell spread of herpes simplex virus by leukocytes. J Exp Med
. 1973;137:706–720.
[CrossRef] [PubMed]Zisman B, Wheelock EF, Allison AC. Role of macrophages and antibody in resistance of mice against yellow fever virus. J Immunol
. 1971;107:236–243.
[PubMed]Ben-Nathan B, Huitinga I, Lustig S, van Rooijen N, Kobiler D. West Nile virus neuroinvasion and encephalitis induced by macrophage depletion in mice. Arch Virol
. 1996;141:459–469.
[CrossRef] [PubMed]Mestan J, Digel W, Mittnacht S, et al. Antiviral effects of recombinant tumour necrosis factor in vitro. Nature
. 1986;323:816–819.
[CrossRef] [PubMed]Ito M, O’Malley JA. Antiviral effects of recombinant human tumor necrosis factor. Lymphokine Res
. 1987;6:309–318.
[PubMed]Hendricks RL, Janowicz M, Tumpey TM. Critical role of corneal Langerhans cells in the CD4− but not CD8− mediated immunopathology in herpes simplex virus-1-infected mouse corneas. J Immunol
. 1992;148:2522–2529.
[PubMed]Chen H, Hendricks RL. B7 costimulatory requirements of T cells at an inflammatory site. J Immunol
. 1998;160:5045–5052.
[PubMed]Nair S, Buiting AM, Rouse RJ, van Rooijen N, Huang L, Rouse BT. Role of macrophages and dendritic cells in primary cytotoxic T lymphocyte responses. Int Immunol
. 1995;7:679–688.
[CrossRef] [PubMed]Sallusto F, Lanzavecchia A. Efficient presentation of soluble antigen by cultured human dendritic cells is maintained by granulocyte/macrophage colony-stimulating factor plus interleukin 4 and downregulated by tumor necrosis factor alpha. J Exp Med
. 1994;179:1109–1118.
[CrossRef] [PubMed]