Impact of a hormone-releasing intrauterine system on the vaginal microbiome: a prospective baboon model.

BACKGROUND: Use of a levonorgestrel-releasing intrauterine system (LNG-IUS) in humans may alter vaginal microbial populations and susceptibility to pathogens. This study evaluated the time-dependent effects of an LNG-IUS on the vaginal microbiome of the baboon, a useful animal model for reproductive studies. METHODS: Levonorgestrel-releasing intrauterine systems were inserted into three reproductively mature, female baboons. The animals were evaluated for 6 months by physical examination and Gram-stained cytology. The vaginal microbiota was characterized at each timepoint by culture-independent analysis of the 16S rRNA-encoding gene. RESULTS: Each baboon harbored a diverse vaginal microbiome. Interindividual variation exceeded intra-individual variation. Diversity declined over time in one baboon and showed mild fluctuations in the other two. There were no significant community differences from early to late post-LNG-IUS placement. CONCLUSIONS: The baboon vaginal microbiome is unique to each individual and is polymicrobial. In this pilot study, the vaginal microbiome remained stable from early to late post-LNG-IUS placement.

Novel genital alphapapillomaviruses in baboons (Papio hamadryas anubis) with cervical dysplasia.

Genital Alphapapillomavirus (αPV) infections are one of the most common sexually transmitted human infections worldwide. Women infected with the highly oncogenic genital human papillomavirus (HPV) types 16 and 18 are at high risk for development of cervical cancer. Related oncogenic αPVs exist in rhesus and cynomolgus macaques. Here the authors identified 3 novel genital αPV types (PhPV1, PhPV2, PhPV3) by PCR in cervical samples from 6 of 15 (40%) wild-caught female Kenyan olive baboons (Papio hamadryas anubis). Eleven baboons had koilocytes in the cervix and vagina. Three baboons had dysplastic proliferative changes consistent with cervical squamous intraepithelial neoplasia (CIN). In 2 baboons with PCR-confirmed PhPV1, 1 had moderate (CIN2, n = 1) and 1 had low-grade (CIN1, n = 1) dysplasia. In 2 baboons with PCR-confirmed PhPV2, 1 had low-grade (CIN1, n = 1) dysplasia and the other had only koilocytes. Two baboons with PCR-confirmed PhPV3 had koilocytes only. PhPV1 and PhPV2 were closely related to oncogenic macaque and human αPVs. These findings suggest that αPV-infected baboons may be useful animal models for the pathogenesis, treatment, and prophylaxis of genital αPV neoplasia. Additionally, this discovery suggests that genital αPVs with oncogenic potential may infect a wider spectrum of non-human primate species than previously thought.

Formulation development of retrocyclin 1 analog RC-101 as an anti-HIV vaginal microbicide product.

RC-101 is a synthetic microbicide analog of retrocyclin, which has shown in vitro activity against X4 and R5 HIV-1. In an effort to develop a safe and effective RC-101 vaginal microbicide product, we assessed safety in ex vivo macaque and human models and efficacy using in vitro and ex vivo models. A polyvinyl-alcohol vaginal film containing RC-101 (100 µg/film) was developed. Formulation assessment was conducted by evaluating disintegration, drug content, mechanical properties, and stability. Efficacy was evaluated by in vitro peripheral blood mononuclear cells (PBMC) assay and ex vivo human ectocervical tissue explant model. Ex vivo safety studies were conducted by exposing RC-101 to an excised monkey reproductive tract and excised human ectocervical tissue. RC-101 100 µg films were shown to be safe to human and monkey tissue and effective against HIV-1 in vitro and ex vivo in human ectocervical tissue. The 90% inhibitory concentration (IC90) for RC-101 films at 2,000 µg (IC90=57.5 µM) using an ex vivo model was 10-fold higher than the IC90 observed using an in vitro model (IC90=5.0 µM). RC-101 films were stable for 1 month at 25°C, with in vitro bioactivity maintained for up to 6 months. RC-101 was developed in a quick-dissolve film formulation that was shown to be safe in an ex vivo model and effective in in vitro and ex vivo models. RC-101 film formulations were shown to maintain bioactivity for a period of 6 months. Findings from the present study contribute to the development of a safe and effective topical microbicide product.

Fine structural localization of potassium-stimulated rho nitrophenylphosphatase activity in denrites of the cerebral cortex.

A histochemical technique for the demonstration of K+-rho-nitrophenylphosphatase (K+-rhoNPPase) activity, a component of the Na+,K+-ATPase, has been applied at the fine structural level in the somatosensory cortex of the rat. Reaction product was consistenly found in dendrites and in association with the cytoplasmic aspect of the dendritic plasmalemma. Reaction product often filled portions of the tubular smooth endoplasmic reticulum in these processes. The results of these studies are interpreted to indicate that enzymatic activity is associated with large-and small-diameter dendrites. No convincing evidence of high activity was found in glial profiles. The importance of neurons and their dendrites in active transport of sodium and potassium ions in the cerebral cortex may be more significant than indicated by studies with isolated neurons and glia.

Time-lapse videomicroscopic study of in vitro wound closure in rabbit corneal cells.

This study used video time-lapse recording to characterize the dynamic features of corneal epithelial cells and keratocytes during in vitro wound closure. Confluent cultures of these two cell types from rabbits were established in Rose chambers. A wound 4 or 10 mm in diameter was produced in the center of each culture by mechanical removal of cells. Wound closure was recorded by videomicroscopy for 2-3 days and reviewed at a playback speed of 400 times normal. The epithelial cells at the wound margin initiated migration by extending lamellipodia with undulatory motions. Successive tiers of cells moved as a continuous sheet in a unified and coordinated manner while maintaining intercellular linkage. The migration was unidirectional, toward the wound center. The mean migration rate of the leading cells was 104 microns/hr. The trailing cells migrated at successively slower rates, inversely proportional to their distance from the wound margin. Mitosis was rare during migration but did occur simultaneously. The mitotic rate was 3.7 mitoses/100 cells. The relative mitotic frequency was 0.23 mitosis/hr. By contrast, in keratocyte cultures, the cells around the wound margin migrated individually and asynchronously without intercellular connection. Initially the cells moved generally toward the wound space, but later, different cells migrated in different directions. The mean migration rate was 15 microns/hr. Mitosis occurred frequently. The mitotic rate was 25.3 mitoses/100 cells, and the relative mitotic frequency was 1.33 mitoses/hr. The cell cycle duration was 9.9 hr. Thus corneal epithelial cells and keratocytes showed fundamentally different characteristics and mechanisms of wound closure in vitro.

Experimentally induced ocular chlamydial infection in infant pig-tailed macaques.

Four Macaca nemestrina monkeys were inoculated in the conjunctiva with Chlamydia trachomatis (strain E) at 6 weeks of age. A fifth monkey was inoculated with HeLa cell materials only. Ten weeks later, all monkeys were reinoculated with either strain E or strain C. All inoculated monkeys were susceptible to infection with C. trachomatis as documented by fluorescent antibody staining of smears and reisolation of the organism from conjunctival and nasopharyngeal swab specimens. Rectal and vaginal swab specimens remained negative throughout the study. Three of four inoculated animals responded with IgM titers reaching a peak of 1:16 (M#3) and 1:32 (M#1, M#4) 2 weeks after the primary inoculation. IgG appeared in all inoculated animals and titers rose to peak levels of 1:64 (M#2), 1:128 (M#1, M#3), and 1:256 (M#4). Histopathology documented a dramatic difference in immunological response following secondary inoculation. Primary inoculation elicited a typical inflammatory response characterized by moderate stromal infiltration of polymorphonuclear and mononuclear leukocytes. Plasma cells appeared by week 3 postinoculation (pi). Following a secondary inoculation, classic follicle formation was evident by 1 week pi. Mononuclear markers identified a germinal center composed of B cells and a T cell cap. Epithelial thinning near the cap of the follicle was accompanied by a complete loss of goblet cells. This model may be useful for studying the immunopathology of infant chlamydial infections.

Experimental trachoma in subcutaneous conjunctival autografts in macaques.

To study chlamydial conjunctivitis, conjunctival autografts subcutaneously implanted in pockets on the abdomens of rhesus (Macaca mulatta) and pig-tailed (M. nemestrina) monkeys were inoculated percutaneously (4-10 X 10(4) inclusion-forming units per pocket) with trachoma strains of Chlamydia trachomatis (serovars B & C). These conjunctival pockets were removed on days 2, 3, 4, 5, 6, 7, 8, 10, 14 and 16 post-inoculation (pi). Tissues (at least two samples at each time interval) were prepared either for reisolation of the organisms by cell culture or histologic examination by light and electron microscopy. Control tissue, inoculated with either HeLa cell material or UV-inactivated organisms, were prepared in parallel. Bloods were drawn and tear strips taken at weekly intervals for 8 weeks. A total of 221 bulbar and 99 palpebral conjunctival pockets were established over time with the success rate of 75% and 88%, respectively, in six rhesus and ten pig-tailed monkeys. Histological examination revealed widespread infiltration of mixed polymorphonuclear and mononuclear cells on days 2 and 3 pi. By day 5 pi, lymphocytes had migrated into the thinned epithelial layer. Patches of inflammatory infiltrate similar to trachoma follicles were observed, although distinct germinal centers were absent. Surface morphologies of normal and infected pocket conjunctiva were examined by scanning electron microscopy. Normal tissue was characterized by a regular mosaic pattern of closely packed epithelial cells containing numerous microvilli. Infected tissue was edematous, and the continuity of the mucosal surface had been altered. Chlamydiae were reisolated from the pockets on days 2, 3, 6, 8 and 10 pi.(ABSTRACT TRUNCATED AT 250 WORDS)

In vitro growth of Chlamydia trachomatis in conjunctival and corneal epithelium.

This study used primary cultures of conjunctival and corneal epithelial cells from rabbit, monkey and humans to investigate the infection process and host interactions of chlamydia. The epithelial cells were isolated from bulbar and palpebral conjunctivae and the cornea following incubation with EDTA or dispase and microdissection. The cells were trypsinized and grown in microtest wells or Rose Chambers (gelatin-coated glass substratum). The cell origin of the cultured epithelial cells was verified by immunofluorescence staining with anticytokeratins. The cells were nonreactive when stained with antivimentin, a fibroblast marker. The growth kinetics of the cultured epithelial cells were determined by morphological criteria. Cells reached confluency by 5-7 days, and remained as such for 18 days. The cells were maintained as long as 32 days in primary culture. After the cells had attained confluency (5-7 days), they were infected with ocular strains B/TW-5/OT or C/TW-3/OT C. trachomatis. Chlamydial inclusions were identified by light and electron microscopy. Direct FITC C. trachomatis staining (species-specific monoclonal antibody) of the inclusions was used to determine the infectivity of the various types of epithelial cells. The dynamics of the infection process was documented by time lapse photomicroscopy. Small inclusions were identified by 18 hr postinoculation (pi). By 48 hr pi, the inclusions had dramatically increased in size, occupying much of the host perikarya. The reticulate bodies were very active at this time. By 70 to 100 hr pi, the inclusions contained the highly infectious elementary bodies. At this time, rupture of the inclusion and lysis of the infected cells usually occurred.(ABSTRACT TRUNCATED AT 250 WORDS)

The effects of Chlamydia trachomatis on the female reproductive tract of the Macaca nemestrina after a single tubal challenge following repeated cervical inoculations.

The effects of repeated cervical infections followed by a single direct tubal inoculation with Chlamydia trachomatis, serovars D and F, were examined in 11 pig-tailed macaques to test the hypothesis that tubal inoculation after cervical priming causes a more severe disease than primary tubal inoculation alone. Animals were cervically inoculated between two and five times. Fallopian tubes were inoculated with serovar D or F 1 week after the last cervical challenge. Three control monkeys received only one direct tubal inoculation without previous cervical inoculation. Infection was confirmed by isolating the microorganism from the endocervix in 13 of 14 monkeys and from the endosalpinx in four only after the tubal inoculation. Antibody was detected in post-infection sera of all 14. Tubal edema occurred in seven of 11 animals after the first cervical inoculation, and uterine erythema occurred in 11 of 11 after the second cervical inoculation. Peritubal adhesions were induced before the tubal inoculation in zero of seven given three or fewer cervical inoculations and four of four given five cervical inoculations (P less than .01). After direct tubal inoculation, peritubal adhesions became more prominent, and the 11 hysterectomy specimens showed plasma cell endometritis in nine and salpingitis in nine. Two control monkeys developed minor adhesions, the other none. One tube in two of three controls showed mild plasma cell infiltrates, whereas no evidence of endometritis was observed in controls. Histopathology in these monkeys was characteristic of chlamydial endometritis and salpingitis. However, the pathogenesis of these changes is uncertain because C trachomatis was not isolated from the endosalpinx after cervical inoculations alone.

Depomedroxyprogesterone-induced hypoestrogenism and changes in vaginal flora and epithelium.

OBJECTIVE: To identify the effects of depomedroxyprogesterone acetate (DMPA) on vaginal microbial flora and epithelium. METHODS: Women who desired DMPA for contraception were evaluated before and at 3 and 6 months after initiation of 150-mg DMPA injections every 3 months. At each visit, we assessed genital symptoms, vaginal signs, vaginal microflora, and histopathology by vaginal biopsies. RESULTS: Among 38 women observed for 6 months, there was significant reduction in mean serum estradiol level (99.9 +/- 9.3 pg/mL to 26.6 +/- 1.6 pg/mL, P <.001). The number of subjects with any Lactobacillus did not change, but the number with hydrogen peroxide (H(2)O(2))-positive Lactobacillus decreased from 20% before to 12% after 6 months of DMPA (P =.005). The log concentration in colony-forming units per milliliter of vaginal fluid of H(2)O(2)-positive Lactobacillus decreased in a linear manner from 4. 0 +/- 0.6 at baseline to 2.5 +/- 0.6 after 6 months of DMPA use (P =. 006). The mean number of cell layers in the epithelium was reduced slightly from 28.1 +/- 0.7 to 25.9 +/- 0.9 (P =.05), epithelial thickness decreased from 1.02 +/- 0.04 mm to 0.89 +/- 0.05 mm (P =. 005), and the glycogen-positive thickness decreased from 0.81 +/- 0. 04 mm at baseline to 0.66 +/- 0.05 after 6 months of DMPA use (P =. 005). CONCLUSION: Depomedroxyprogesterone acetate produced a systemic hypoestrogenic state associated with decreased H(2)O(2)-positive Lactobacillus colonization and slight thinning of the glycogen vaginal epithelial layer. Such changes possibly compromise the vaginal barrier to infection.

A comparison of the fallopian tube's response to overt and silent salpingitis.

We examined two groups of infertile women who underwent microsurgical repair of their fallopian tube(s) for distal tubal obstruction, one with a history of salpingitis (overt pelvic inflammatory disease) (N = 34) and one without (silent pelvic inflammatory disease) (N = 25). Nine women with normal tubes undergoing hysterectomy and salpingectomy served as controls. Tubal biopsy specimens were studied by light, scanning, and transmission electron microscopy to assess tubal damage. Morphologic damage was scored 0-9, with 0 representing normal tubal architecture and 9 assigned to severe tubal damage. The mean score (+/- SEM) in women with overt pelvic inflammatory disease was 4.2 +/- 0.4; in women with silent pelvic inflammatory disease, 4.3 +/- 0.4; and in the control group, 0.76 +/- 0.2 (P less than .001). Fallopian tube abnormalities seen in women with overt and silent pelvic inflammatory disease included flattened mucosal folds, extensive deciliation, and degeneration of secretory epithelial cells, morphologic changes that are similar to the cellular changes observed in our experimental Chlamydia trachomatis infections in monkeys. Laser light-scattering spectroscopy was used to measure the ciliary activity of the epithelial cells. Ciliary beat frequency was significantly reduced in women with overt pelvic inflammatory disease (N = 13; f = 6.4 +/- 1.2 Hz) and in women with silent pelvic inflammatory disease (N = 11; f = 7.2 +/- 1.2 Hz) as compared with the controls (N = 5; f = 23.4 +/- 1.5 Hz) (P less than .001).(ABSTRACT TRUNCATED AT 250 WORDS)

Salpingoscopy: light microscopic and electron microscopic correlations.

In order to examine the ability of salpingoscopy to diagnose intratubal pathology, 32 fallopian tubes were evaluated salpingoscopically and histologically. Both flexible and rigid salpingoscopes were used, and observations were documented by intratubal photography. Salpingoscopic criteria were established and each criterion assigned a numerical value. Each tube was evaluated for patency, mucosal fold architecture, erythema, adhesions, and dilatation. Based on these criteria, tubes were graded as normal or as abnormal with mild, moderate, or severe changes. Histologically, each tube was evaluated for patency, epithelial changes, vascularity, dilatation, adhesions, and active inflammation. Six tubes with significant histologic findings and two histologically normal fallopian tubes were also examined by transmission electron microscopy. In five discordant cases, histology revealed epithelial and stromal changes not detected by salpingoscopy. Fallopian tubes with severe disease were diagnosed by both methods. Transmission electron microscopy of histologically abnormal tubes showed flattening of the epithelium with markedly reduced ciliary distribution, degenerating secretory epithelial cells with large intracellular vacuoles, and swollen nuclei containing sparse chromatin. Our results indicate that salpingoscopic observations are consistent with histologic findings when endotubal disease is severe. However, moderate pathologic changes as documented by light microscopy and transmission electron microscopy were frequently not diagnosed salpingoscopically, even with magnification.

Mechanically-induced hydrosalpinx: long-term oviductal dilatation does not impair ciliary transport function.

Long-term hydrosalpinges were mechanically induced in rabbits by ligation of the fimbriated end of the oviduct. The structure and function of these model hydrosalpinges were studied 28 to 52 weeks following ligation. This procedure caused a nonpurulent, clear serous fluid to accumulate within the lumen of the ampulla, which resulted in dilatation of the ampulla and thinning of the tubal wall. The intraluminal mucosal folds were attenuated in the expanded regions; however, normal ciliation was predominant throughout the endosalpinx. Two rabbits, one with a single distal tubal ligation and the other with double ampullary ligation, showed abnormal epithelium with distinct patches of flattened polygon-shaped, nonciliated cells. In vivo and in vitro observations of luminal transport of surrogate ova in cumulus showed that ciliary transport was not affected by the long-term gross distension of the ampullae. The authors conclude that long-term tubal dilatation by itself does not alter tubal morphology sufficiently to impair ovum transport function in the oviductal ampulla.

Hydrosalpinx: effect of oviductal dilatation on egg transport.

Ligation of the ovarian end of the oviduct was used to induce hydrosalpinges in rabbits and monkeys. This procedure resulted in an accumulation of clear serous fluid within the lumen and distention of the ampullary wall. The ampullary endosalpinx responded with a general flattening of the surface architecture, especially a decrease in the prominence of the longitudinal mucosal folds. However, this flattened epithelial surface showed normal ciliation. Two to five months after ligation, direct observations were made in vivo of luminal transport of cumulus egg masses and surrogates. These observations were followed by study in vitro of ciliary currents on the exposed luminal surface. The results demonstrated conclusively that tubal dilatation had no adverse effect on cilia-mediated ovum transport within the ampulla. The implication of these results in terms of tubal infertility is discussed.

Egg transport in the rabbit oviduct following ampullary resection and microsurgical end-to-end anastomosis.

Surgical alteration of rabbit oviducts was employed to investigate the mechanisms of ovum transport. Resection of a 5- to 10-mm segment of midampulla was followed by microsurgical end-to-end anastomosis. One to two months later, direct observations were made, in situ, of ampullary egg transport. Stained cumulus masses were transported normally to the site of anastomosis: two-thirds of those studied were delayed at that point for an average of 2 1/2 minutes. Normal transport then resumed and continued to the ampullo-isthmic junction. In all but one instance, blockage of muscular activity with isoproterenol prevented transport beyond the anastomosis site, demonstrating the presence of an obstacle to ciliary transport. These studies reveal an important facilitative role for muscle in improving the reliability of ampullary egg transport. Considering species differences in egg transport mechanisms, it is suggested that ampullary-ampullary anastomosis in women might have a poor prognosis for re-establishing fertility.

Eelectron microscopic examination of the rabbit oviductal ampulla following microsurgical end-to-end anastomosis.

The endosalpinx of both normal and microsurgically reconstructed ampullae in rabbit oviducts was examined by scanning and transmission electron microscopy following ovum transport studies. Tall, longitudinal mucusal folds ran continuously throughout the lumina of normal ampullae and were clearly interrupted at the incision site in the reconstructed oviducts. In both normal and surgically repaired tubes the endosalpinx was covered with long, slender cilia and bulbous processes of secretory cells with microvillous surfaces. Intracellular examination of these epithelial cells suggested no abnormal structure or function. These observations indicate that the epithelium on the severed ends of the endosalpinx healed completely within 1 month following ampullary anastomosis. Since no luminal obstruction was observed, the interruption and misalignment of the mucosal folds appear to be the cause of the impaired ciliary transport of cumulus masses observed in these oviducts. When species differences in tubal structure and function are considered, it appears likely that ampullary-ampullary anastomosis could hinder egg transport and fertility in women.

PIP: Scanning and transmission electron microscopy were used to study the endosalpinx of both normal and microsurgically reconstructed ampullae in rabbit oviducts; the ampullae examined had been used in ovum transport studies. The lumina of normal ampullae showed tall longitudinal mucosal folds which ran continuously throughout the organ; these mucosal folds were clearly interrupted at the site of incision in reconstructed specimens. In both normal and surgically repaired tubes, long slender cilia and bulbous processes of secretory cells with microvillous surfaces covered the endosalpinx. These epithelial cells showed no abnormal structure or function upon intracellular examination. Therefore, it seems that the epithelium on the severed ends of the endosalpinx healed completely within 1 month of ampullary reanastomosis. The interruption and resulting misalignment of the mucosal folds seem responsible for the impaired ciliary transport of cumulus masses through oviducts since no luminal obstruction was observed. Though these experiments were performed in rabbit oviducts, it seems likely that ampullary-ampullary anastomosis in women could hinder ovum transport and fertility.

Function and structure of the rabbit oviduct following fimbriectomy. I. Distal ampullary salpingostomy.

The fimbria has long been considered an indispensable portion of the fallopian tube. To test this hypothesis, the fimbria and up to one-half of the adjoining ampulla of the left oviduct were resected by microsurgery in 13 New Zealand White does. The remaining distal ampulla was subjected to a cuff salpingostomy. Following a convalescence of 4 to 8 weeks and induced ovulation, 6 of the 11 resected oviducts apprehended ova and 29% of the total number ovulated ipsilaterally, whereas the right control oviducts retrieved 77% of the corresponding ova. Direct observation in vivo showed that the ova adhered to the neofimbria and that subsequent transport across the everted, hypertrophied ampullary mucosal folds into the tubal lumen took place readily. Scanning electron microscopy of the "neofimbria" and adjoining distal ampulla demonstrated populations of ciliated and secretory cells that were similar to those of the contralateral intact fimbria. This information challenges the concept of fimbrial indispensability and depicts the fimbriated ostium of a distal ampullary cuff salpingostomy as having an adequate function, albeit less efficient than normal

Experimental salpingitis in rabbits provoked by Chlamydia trachomatis.

Experimental salpingitis was studied by the introduction of Chlamydia trachomatis, immunotype D, directly into the oviducts of New Zealand White rabbits. Some rabbits were rechallenged with immunotype F to elicit a second infection. Both experiments produced self-limited acute salpingitis. Light microscopy (LM) and transmission electron microscopy (TEM) showed an extensive polymorphonuclear leukocytic infiltration in the submucosa and mucosa. Scanning electron microscopy (SEM) revealed various alterations of the endosalpingeal surface, including deciliation and flattening of the epithelial cells. These morphologic changes were more pronounced following rechallenge. High and long-lasting serum antibody titers were observed in those rabbits receiving intratubal inoculation of live infectious organisms; no response was evident when inactivated organisms were used. These results indicate that the rabbit is useful in the study of the effects of infection on oviductal function.

A comparison between argon laser and microsuture anastomosis of the rat uterine horn.

For assessment of the use of the argon laser for tubal anastomosis, the uterine horns of 12 Sprague-Dawley rats were surgically divided and then anastomosed, 6 by argon laser photocoagulation and 6 by the conventional technique of microsurgery. After a 4- to 6-week postsurgical period subjects were reexamined. All microsutured anastomoses were fully patent and continuous, with no apparent fibrosis. Four of six laser subjects had complete occlusion; the other two exhibited patencies between 10% and 20% of normal luminal area. Although initially producing satisfactory union, argon laser photocoagulation proved highly tissue traumatic, resulting in poor regeneration of the anastomotic site.

Host response to primary Chlamydia trachomatis infection of the fallopian tube in pig-tailed monkeys.

Experimental acute salpingitis was produced in four pig-tailed monkeys, Macaca nemestrina, by intratubal inoculation with Chlamydia trachomatis (serotypes E or F). The organisms were reisolated from both the endosalpinx and endocervix as early as 1 week after the original inoculation. Endosalpinx cellular responses to the infection were examined by light, transmission, and scanning electron microscopy. A moderate lymphocyte infiltration was detected in the submucosa on day 7. By days 14 and 21 the lymphocytic infiltration was heavy and extended into both the submucosa and the mucosa; the infiltration subsided by day 35. Epithelial cell degeneration occurred in close approximation to lymphocytes, suggesting the immunologic basis of tissue destruction. Scanning electron microscopy revealed extensive deciliation and increased plasmalemmal alterations of nonciliated cells. The presence of C. trachomatis in frozen and deparaffinized tissues was demonstrated by immunofluorescence and immunoperoxidase staining with monoclonal antibody to C. trachomatis. Only secretory cells contained chlamydial inclusions. A humoral immune response to C. trachomatis was demonstrated by microimmunofluorescence. No histologic or immunologic evidence of infection was present in two control monkeys inoculated with HeLa cell material. The histopathologic and immunologic findings of this study establish the pig-tailed monkey as a useful model for further studies of the pathogenesis and pathophysiology of chlamydial salpingitis.