Two-fraction carbon ion radiotherapy for hepatocellular carcinoma

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Background: In Japan, most patients with Hepatocellular Carcinoma (HCC) have liver cirrhosis, an advanced hepatic disorder, and they often require repeated therapies owing to the multicentric nature of carcinogenesis in the cirrhotic liver. Therefore, both radical effect and minimal invasiveness are essential for the treatment of HCC. However, there were no therapies satisfying both of these essential requirements for every-sized HCC. The purpose of this trial was to evaluate the safety and efficacy of two-fraction carbon ion radiotherapy (CIRT) for HCC. Methods: Eligibility criteria for this study were as follows: biopsy-proven HCC; recurrent or residual tumor after other ineffective treatments or no indication for any other treatment; no prior radiotherapy for target tumors; hepatic disorder of Child-Pugh grade A or B; Karnofsky performance status of 60–100; no other active cancer; and digestive tract not in contact with clinical target volume. CIRT was administered within dose escalation study of 32.0 to 38.8 cobalt gray equivalent (GyE) in 2 fractions for 2 days. Results: Between April 2004 and August 2006, 40 patients were totally enrolled. All patients had chronic liver diseases of Child-Pugh grade A in 37, B in 3. The median tumor size was 4.7 cm in diameter (2.0 to 6.7 cm). During a median follow-up of 32 months (range, 5–45 months), no hepatic failure resulting from the therapy and no treatment-related death occurred. Incidence of grade 3 early hepatic toxicity according to NCI-CTC ver.2 in the essential valuables concerning hepatic function was 0% in serum-GPT, ALB, prothrombin activity (PT%) and ALP, and 3% in T.BIL. No grade 4 toxicity has occurred. In 94% and 86% out of the patients, Child-Pugh score did not increase by more than 1 point in the early and late phases, respectively. In the lower-dose group (32.0, 33.6, 35.2 GyE: n=18), 2-year local control rate and overall survival rate were 71% and 83%, respectively. In the higher-dose group (37.0, 38.8 GyE: n=22), they were 100% and 90%, respectively. Conclusions: Although 2-fraction carbon ion radiotherapy seems to be safe and effective, and to have a promising potential as a new, radical, and minimally invasive therapeutic option for Hepatocellular Carcinoma, further careful follow-up is needed to confirm it’s clinical efficacy.

No significant financial relationships to disclose.

Anti-parietal cell antibody and serum pepsinogen assessment in screening for gastric carcinoma

BACKGROUND

Anti-parietal cell antibody is found in patients with Helicobacter pylori-positive gastritis and is related to atrophic gastritis and gastric carcinoma.

AIM

To identify the characteristics of patients at high-risk for gastric carcinoma in terms of anti-parietal cell antibody and serum pepsinogen.

PATIENTS AND METHODS

Subjects were 92 H. pylori-positive patients (54 men, 38 women; mean age, 57.9 years; range, 15-88 years). The serum concentrations of pepsinogen I and II were determined by radioimmunoassay, and the presence of anti-parietal cell antibody was assessed by enzyme-linked immunosorbent assay. Degrees of inflammation and atrophy in the corpus of the stomach were evaluated histologically.

RESULTS

Patients were classified into four groups according to anti-parietal cell antibody status and pepsinogen I/II ratio. Anti-parietal cell antibody-negative/pepsinogen I/II-low patients had the highest risk for gastric carcinoma (prevalence of gastric carcinoma: 7/13=53.8%, odds ratio=7.6, 95% confidence interval, 1.2-48.0). Anti-parietal cell antibody titre was high when inflammation in the corpus was severe (p=0.06) and significantly low when atrophy in the corpus was severe (p=0.01).

CONCLUSION

Our results showed that patients with a negative anti-parietal cell antibody titre and low pepsinogen I/II ratio are at high-risk for gastric carcinoma.

Famotidine prevents canine gastric blood flow reduction by NSAIDs

AIM

To investigate the effect of famotidine on gastric blood flow reduction induced by diclofenac sodium, a common non-steroidal anti-inflammatory drug in Japan, using laser Doppler flowmetry in the canine stomach.

METHODS

The gastric mucosal blood flow was measured by laser Doppler flowmetry in 15 healthy male beagles before and 60 min after the administration of diclofenac suppository (1.0 mg/kg) into the rectum. The examination was done in a crossover, single-blinded fashion. All dogs underwent both famotidine (0.5 mg/kg) and placebo (saline) injection simultaneously with the administration of diclofenac. In addition, the tissue concentration of prostaglandin E2 was measured.

RESULTS

The blood flow decreased by 18.3 +/- 9.1% in the gastric body, by 26.3 +/- 8.1% in the antrum in the placebo group after the administration of diclofenac sodium, while the decreases seen were significantly smaller in the famotidine group: 3.2 +/- 12.6% in the gastric body and 7.9 +/- 16.5% in the antrum (P = 0.001 for the gastric body, P = 0.0034 for the antrum). Conversely, the percentage of mucosal prostaglandin E2 concentration decrease in each group did not show a significant difference.

CONCLUSION

Famotidine alleviates the reduction of gastric blood flow induced by diclofenac sodium. Further, not only mucosal prostaglandins but also gastric acid may play an important role in non-steroidal anti-inflammatory drugs-induced gastric microcirculatory disturbance.

Effect of long-term half-dose famotidine therapy on corpus gastritis in peptic ulcer disease

BACKGROUND

Recent studies showed that acid-suppressive therapy aggravates corpus gastritis in patients with Helicobacter pylori infection.

AIM

The aim of this study was to evaluate the effect of famotidine, a histamine receptor antagonist on corpus gastritis in patients with peptic ulcer disease.

METHODS

We enrolled 287 patients, 173 with duodenal ulcer and 114 with gastric ulcer and 100 patients with H. pylori-positive gastritis as control subjects. Patients with peptic ulcer were classified according to whether or not they received famotidine-maintenance therapy (20 mg/day) after primary treatment. At the time of endoscopy, biopsy specimens were obtained from the antrum and the corpus. The degrees of neutrophil and lymphocyte infiltration, atrophy and intestinal metaplasia were scored according to the updated Sydney System.

RESULTS

The degrees of neutrophil infiltration and atrophy in the corpus were significantly less in patients with gastric ulcer or duodenal ulcer than in patients with H. pylori-positive gastritis (P < 0.01). Differences in the degrees of neutrophil infiltration and atrophy in the corpus between the non-maintenance group and the maintenance group were not significant.

CONCLUSION

Long-term therapy with famotidine does not appear to lead to an increase in the incidence of corpus gastritis or corpus atrophy in patients with peptic ulcer disease.

Effect of famotidine on recurrent bleeding after successful endoscopic treatment of bleeding peptic ulcer

AIM

We investigated the effect of acid suppression therapy on recurrent bleeding after successful endoscopic treatment of bleeding peptic ulcer.

METHODS

A total of 400 patients with bleeding peptic ulcer received either intravenous infusion of famotidine (40 mg/day) (n = 207, 163 males, 44 females, mean age 61.5 years) or drip infusion of omeprazole (40 mg/day; n = 193, 134 males, 59 females, mean age 59.8 years) after successful endoscopic treatment. The fasting duration, hospital stay, volume of transfused blood, incidence of rebleeding and mortality were compared between the two groups.

RESULTS

The incidence of rebleeding did not differ significantly between the famotidine group (9%) and the omeprazole group (8%). The mean hospital stay was significantly shorter in the omeprazole group (18.4 days) than in the famotidine group (21.5 days, P = 0.009). However, there was no statistically significant difference in fasting duration, volume of transfused blood or mortality.

CONCLUSION

Our findings indicate that intravenous infusion of famotidine after successful endoscopic treatment is equivalent to drip infusion of omeprazole for prevention of recurrent bleeding.

Clinical features of gastric cancer discovered after successful eradication of Helicobacter pylori: results from a 9-year prospective follow-up study in Japan

BACKGROUND

Eradication of Helicobacter pylori is expected to prevent the development of gastric cancer. However, gastric cancer is sometimes discovered after successful eradication of H. pylori.

AIM

To conduct a prospective study to determine the clinical features of patients who underwent successful eradication and were later diagnosed with gastric cancer.

METHODS

A total of 1787 patients (1299 males and 488 females; mean age, 58.2 years; range: 15-84) who underwent successful eradication therapy between April 1994 and March 2001 were our study subjects.

RESULTS

Gastric cancer occurred at a rate of 1.1% (20 of 1787) during the follow-up period. Gastric cancer comprises six of 105 (5.7%) with early gastric cancer after endoscopic resection, 12 of 575 (2.1%) with gastric ulcer and two of 453 (0.4%) with atrophic gastritis. Gastric cancer did not develop in any patient with duodenal ulcer. All patients with gastric cancer had baseline severe atrophic gastritis in the corpus.

CONCLUSION

Careful endoscopic examination is necessary even after successful eradication of H. pylori in patients with early gastric cancer or gastric ulcer with severe mucosal atrophy in the corpus.

Eradication of Helicobacter pylori increases the incidence of hyperlipidaemia and obesity in peptic ulcer patients

BACKGROUND

Eradication of Helicobacter pylori improves clinical symptoms and quality of life in patients with peptic ulcer.

AIM

To investigate the effect of eradication of H. pylori on body mass index and incidence of hyperlipidaemia in patients with peptic ulcer.

PATIENTS AND METHODS

The study population comprised 50 patients (42 men, 8 women; mean age, 51 years; 28 gastric ulcer, 22 duodenal ulcer) who underwent physical and blood examination before and 1 year after undergoing eradication therapy and 100 sex- and age-matched control subjects. Body mass index, total cholesterol and triglyceride were measured before and 1 year after therapy.

RESULTS

The eradication therapy group showed a significant increase in body mass index (22.7+/-2.5 kg/m2 before eradication versus 23.6+/-2.6 kg/m2 after eradication, p < 0.01), serum total cholesterol (204.1+/-33.2 mg/dL versus 221.2+/-38.8 mg/dL, p < 0.01), and triglyceride. Additionally, the eradication therapy group showed a significant increase in the incidence of hypercholesterolemia (30% versus 58%, p<0.01), hypertriglyceridaemia (28% versus 44%, p < 0.01) and obesity (12% versus 22%, p <0.05) 12 months after therapy.

CONCLUSION

Our findings show that eradication of H. pylori significantly increases the incidence of hyperlipidaemia and obesity in patients with peptic ulcer.

Effect of Sarsaponin on Ruminal Fermentation with Particular Reference to Methane Production in Vitro

This experiment was designed to investigate the effects of different concentrations (0, 1.2, 1.8, 2.4, and 3.2 g/L) of sarsaponin on ruminal microbial methane production using the substrates soluble potato starch, cornstarch, or hay plus concentrate (1.5:1). Ruminal fluid was collected from a dairy cow, mixed with phosphate buffer (1:2) and incubated (30 ml) anaerobically at 38 degrees C for 6 and 24 h with or without sarsaponin. Excluding the lower level of sarsaponin, pH of the medium was slightly decreased. Ammonia-N concentration and numbers of protozoa were decreased in a dose-dependent manner. Total volatile fatty acids and total gas production were increased. Molar proportion of acetate was decreased and propionate was increased with a corresponding decrease in acetate:propionate ratio. Hydrogen production was decreased. As the concentration of sarsaponin increased from 1.2 to 3.2 g/L, fermentation of soluble potato starch, cornstarch, or hay plus concentrate decreased methane production from 20 to 60% (6 h) and 17 to 50% (24 h), 21 to 58% (6 h) and 18 to 52% (24 h), and 23 to 53% (6 h) and 15 to 44% (24 h), respectively. Excluding the lower dose concentration (1.2 g/L) of sarsaponin, in vitro disappearance of dry matter of hay plus concentrate was decreased after 24 h. In conclusion, these results show that sarsaponin stimulated the mixed ruminal microorganism fermentation as well as to inhibit methane production in vitro.

The long-term effect of Helicobacter pylori eradication therapy on symptoms in dyspeptic patients with fundic atrophic gastritis

AIM

To investigate whether curing Helicobacter pylori infection improves symptoms over the long-term in Japanese patients with nonulcer dyspepsia and fundic atrophic gastritis.

METHODS

Ninety H. pylori-positive dyspeptic patients with fundic atrophic gastritis were enrolled in this study. We performed a randomized double-blind placebo-controlled trial comparing triple therapy (n=45) with that of placebo alone (n=45). Inflammation and mucosal atrophy were scored according to the Updated Sydney System. Symptoms were scored on a scale of 0 to 3 for six items. Fasting samples of gastric juice were taken before endoscopy, and gastric pH was determined. Serum gastrin and pepsinogen levels were measured, and body mass index was determined. These patients were followed up for 3 years, and all measures were evaluated both before and after therapy.

RESULTS

Significant improvement in dyspeptic symptoms and gastritis scores, significant decrease in gastric pH, and significant increase in body mass index were found after 3 years eradication in nonulcer dyspepsia patients treated successfully for H. pylori infection. There were no significant changes in the placebo group.

CONCLUSION

Our study shows that eradicating of H. pylori results in significant long-term reduction in symptoms of nonulcer dyspepsia with fundic atrophic gastritis.

The specific expression of hypoxia inducible factor-1alpha in human gastric mucosa induced by nonsteroidal anti-inflammatory drugs

BACKGROUND

Hypoxia is a cause of gastric mucosal damage induced by nonsteroidal anti-inflammatory drugs (NSAIDs). The expression of hypoxia inducible factor-1alpha (HIF-1alpha) reflects the status of tissue ischaemia.

AIM

To investigate the effect of NSAID administration on the expression of HIF-1alpha in human gastric mucosa.

METHODS

We employed 71 patients including 14 with NSAID administration. The HIF-1alpha expression was estimated by immunohistochemistry using monoclonal antibody (H1alpha67) and raised antiserum (HI-3). Vascular endothelial growth factor expression was also examined by immunohistochemistry. HI-3 recognized hypoxia-induced protein in HeLa cells.

RESULTS

In human gastric mucosa, HIF-1alpha was mainly expressed in the nuclei of the surface epithelial cells and in the neck zone both by use of HI-3 and of H1alpha67. The expression of vascular endothelial growth factor correlated well with that of HIF-1alpha. The level of HIF-1alpha in the surface epithelium was significantly higher in patients with administration of NSAIDs than those without NSAID use (P < 0.001) both in the gastric corpus and antrum. Helicobacter pylori infection did not affected the levels of HIF-1alpha. Long-term administration of rebamipide reduced the level of HIF-1alpha.

CONCLUSION

HIF-1alpha expression is a new biological marker of ischaemia especially in NSAID-related gastric lesions.

Initial medical management of patients severely irradiated in the Tokai-mura criticality accident

A nuclear criticality accident occurred in Japan on September 30, 1999, which resulted in severe exposure of three victims to mixed flux of neutrons and gamma-rays. Estimated average doses for the three victims were 5.4 Gy of neutrons and 8.5 Gy of gamma-rays for Patient A, 2.9 Gy of neutrons and 4.5 Gy of gamma-rays for Patient B, and 0.81 Gy of neutrons and 1.3 Gy of gamma-rays for Patient C. They then suffered the consequences of the effects of ionizing radiation resulting in acute radiation syndrome. In Patients A and B, bone marrow failure was so severe that they received haematopoietic stem cell transplantation. The graft initially took successfully in both patients, although in Patient B it was later taken over by his own haematopoietic cells. They also suffered from severe skin lesions, later exhibited gastrointestinal bleeding and eventually died of multiple organ failure 82 and 210 days after the accident, respectively. The survival of these patients beyond the period of agranulocytosis means that bone marrow failure per se caused by exposure to ionizing radiation may now be overcome. Patient C also developed bone marrow failure and was treated with granulocyte colony-stimulating factor as well as supportive care. He recovered without major complications and is now under periodical follow-up. Remarkably, during the prodromal phase, all the patients exhibited hypoxaemia, two of whom also showed interstitial oedema of the lungs. In Patient C these manifestations improved within a week. The circumstances of the accident and the initial medical treatment of the victims are described.

[A giant left atrial myxoma with severe mitral valve regurgitation: report of a case]

A 76-year-old female underwent operation with a diagnosis of a left atrial myxoma with accompanied mitral regurgitation. Although no clinical findings of mitral regurgitation were noticed preoperatively, degenerative changes to the anterior leaflet as well as chordae tendinae possibly due to mechanical damage by the movement of the giant tumor through the mitral valve complex were observed in operation. Resection of the tumor and mitral valve replacement were successfully performed. Our case suggests that it is indispensable to investigate the mitral valve during operation even in case of the left atrial tumor with no preoperative findings of mitral regurgitation.

Successful treatment for leg ulcers due to hydroxyurea in a patient with chronic myelogenous leukaemia

A 51-year-old male who had intractable leg ulcers during treatment for chronic myelogenous leukaemia with hydroxyurea (HU) is reported. His leg ulcers were treated by application of tretinoin tocoferil (TT) ointment after surgical debridement; good results were obtained. Although stopping HU administration is vitally important, surgical debridement and TT application are effective for treating leg ulcers due to HU.

Helicobacter pylori eradication therapy improves atrophic gastritis and intestinal metaplasia: a 5-year prospective study of patients with atrophic gastritis

AIM

: To investigate the effect of the eradication of Helicobacter pylori on histological gastritis.

METHODS

: Twenty-six patients with moderate to severe atrophy received successful eradication therapy of H.pylori. Four patients dropped out and 22 were followed up prospectively for 5 years. The grades of gastritis were estimated from gastric biopsy specimens. The grade of intestinal metaplasia was also evaluated by dye-endoscopy using methylene blue (methylthioninium chloride). The serum levels of pepsinogen, gastrin and anti-parietal cell antibody were also determined.

RESULTS

: The grades of atrophy decreased in patients with successful eradication therapy in the gastric corpus (before vs. 5 years after eradication, 2.09 +/- 0.15 vs. 0.91 +/- 0.17; P < 0.01) and in the antrum (2.14 +/- 0.17 vs. 1.36 +/- 0.17; P < 0.01). The levels of intestinal metaplasia were also decreased in the corpus (0.91 +/- 0.24 vs. 0.50 +/- 0.16; P < 0.05) and in the antrum (1.41 +/- 0.20 vs. 1.00 +/- 0.16; P < 0.05), which was also demonstrated by the methylene blue (methylthioninium chloride) staining method (33.4 +/- 8.2% vs. 23.0 +/- 6.5%; P < 0.05). The improvement of corpus atrophy correlated well with the high serum level of pepsinogen I (P = 0.005), but showed no correlation with the levels of anti-parietal cell antibody.

CONCLUSIONS

: These results suggest that gastric atrophy and intestinal metaplasia are reversible events in some patients.

Antigen presentation by murine peritoneal cavity macrophage-derived dendritic cells

Murine peritoneal cavity macrophage derived dendritic cells (PEC-DC) generated using early growth factors, interleukin 4 and granulocyte-macrophage colony-stimulating factor followed by maturation in interferon-gamma plus either, Toxoplasma lysate antigen (TLA) or lipopolysaccharide, bind TLA by a nonspecific mechanism and continue to express major histocompatibility complex class II antigens after 24 h of culture in vitro. Moreover, the proliferation of CD3+ spleen T cells from mice immunized with Toxoplasma gondii homogenate, induced by PEC-DC-mediated antigen presentation was statistically significant and of consistent amplitude. This accessory function of PEC-DC is antigen specific.

Role of anti-parietal cell antibody in Helicobacter pylori-associated atrophic gastritis: evaluation in a country of high prevalence of atrophic gastritis

BACKGROUND

Helicobacter pylori plays an important part in the progression of atrophic gastritis; however, markers for predicting the progression of atrophic gastritis remain unidentified. We investigated the relation between the degree of atrophic gastritis and the amount of anti-parietal cell antibodies (APCAs) present.

METHODS

In 219 Japanese patients, APCA was investigated by enzyme-linked immunosorbent assay (ELISA) and by Western blotting. The grade of corpus atrophy was estimated by histology and serum pepsinogen levels. Serum levels of pepsinogen were evaluated by radioimmunoassay.

RESULTS

Helicobacter pylori infection did not affect the APCA levels determined by ELISA. Long-term administration of proton-pump inhibitors and H. pylori eradication did not influence the levels of APCAs. However, in H. pylori-positive patients, the levels of APCA determined by ELISA were statistically higher in patients with severe atrophy than in those with mild atrophy as determined histologically (0.67+/-0.48 versus 0.45+/-0.40; A492, mean+/-s, P=0.01) and serologically by pepsinogen levels (0.66+/-0.51 versus 0.44+/-0.40. P=0.002). The levels of pepsinogen I/II ratio were correlated with APCA levels only in the H. pylori-positive group. Western blotting showed that major antigen was identical with the beta-subunit of H+,K+-ATPase.

CONCLUSION

APCA plays an important part in the progression of corpus atrophy after H. pylori infection.

Relationship between evaluation by quantitative fatty acid myocardial scintigraphy and response to beta-blockade therapy in patients with dilated cardiomyopathy

Predicting the effect of beta-blockade therapy on the clinical outcome of patients with dilated cardiomyopathy (DCM) is difficult prior to the initiation of therapy. Myocardial fatty acid metabolism has been shown to be impaired in patients with DCM. We examined whether the extent of myocardial injury, as assessed by iodine-123 15-( p-iodophenyl)-3- R, S-methylpentadecanoic acid (BMIPP) myocardial scintigraphy, is related to the response of patients with DCM to beta-blockade therapy. Thirty-seven patients with DCM were examined using BMIPP myocardial scintigraphy before and after 6 months of treatment with metoprolol. Myocardial BMIPP uptake (%BM uptake) was estimated quantitatively as a percentage of the total injected count ratio. The left ventricular end-diastolic and end-systolic dimensions (LVDd, LVDs) and ejection fraction (LVEF) were also evaluated. The patients were divided into two groups according to their functional improvement (>10% elevation of LVEF) after 6 months of metoprolol therapy. Twenty-eight patients responded to the therapy, while nine did not. Prior to the therapy, no significant differences in LVDd, LVDs or LVEF were observed between the responders and non-responders. However, the %BM uptake was significantly lower in the non-responders than in the responders (1.0%+/-0.2% vs 2.1%+/-0.5%, P<0.001). The %BM uptake could be used to distinguish the responders from the non-responders with a sensitivity of 0.93 and a specificity of 1.00 at a threshold value of 1.4. After the metoprolol therapy, the %BM uptake improved significantly in the responders (2.5%+/-0.5%, P<0.01) but did not change in the non-responders. These results indicate that myocardial BMIPP uptake could predict the response of DCM patients to beta-blockade therapy.

Comparison of the accessory activity of murine peritoneal cavity macrophage derived dendritic cells and peritoneal cavity macrophages in a mixed lymphocyte reaction

A detailed comparison of the accessory cell activities was carried out among murine peritoneal cavity macrophages (PEC-Mphi), peritonea] cavity macrophages stimulated with granulocyte-macrophage colony stimulating factor (GM-CSF) plus interleukin 4 (IL-4), the most popular cytokine combination widely used to generate dendritic cells (DC) and peritoneal cavity macrophage-derived DC (PEC-DC) using a two-way mixed lymphocyte reaction (MLR). All the cell types used efficiently induced statistically significant naïve T cell proliferation at all culture time points and responder:stimulator ratios used. However, marked differences were noted in the magnitude of the proliferative responses. These variations may be attributed to the intensity of expression of MHC class II glycoproteins, as well as the actual numbers of MHC class II+ cells.

Mitochondrial coupling factor 6 as a potent endogenous vasoconstrictor

We demonstrated recently that coupling factor 6, an essential component of the energy-transducing stalk of mitochondrial ATP synthase, suppresses the synthesis of prostacyclin in vascular endothelial cells. Here, we tested the hypothesis that coupling factor 6 is present on the cell surface and is involved in the regulation of systemic circulation. This peptide is present on the surface of CRL-2222 vascular endothelial cells and is released by these cells into the medium. In vivo, the peptide circulates in the vascular system of the rat, and its gene expression and plasma concentration are higher in spontaneously hypertensive rats (SHRs) than in normotensive controls. Elevation of blood pressure with norepinephrine did not affect the plasma concentration of coupling factor 6. Intravenous injection of recombinant peptide increased blood pressure, apparently by suppressing prostacyclin synthesis, whereas a specific Ab to coupling factor 6 decreased systemic blood pressure concomitantly with an increase in plasma prostacyclin. Interestingly, the antibody's hypotensive effect could be abolished by treating with the cyclooxygenase inhibitor indomethacin. These findings indicate that mitochondrial coupling factor 6 functions as a potent endogenous vasoconstrictor in the fashion of a circulating hormone and may suggest a new mechanism for hypertension.

Ontogeny of pig discrete Peyer's patches: distribution and morphometric analysis

We investigated the development of lymphoid and non-lymphoid cells in discrete Peyer's patches (PP) of the pig using immuno-histology and image analysis. In newborn piglets discrete PP were mainly populated by CD2+, CD3+ T cells, and major histocompatibility complex class II+ cells, many of which were of macrophage and dendritic cell lineage. Four days after birth, cells were localized in defined regions: the follicle; the inter-follicular area and the dome region. Compartmentalization within the follicle started about 6 days after birth. The first signs of secondary follicles were seen from about 14 days. The pig discrete PP attained their mature structure at about 3 weeks after birth. Here we show that despite the demonstration at birth of the cell types that support antigen processing and presentation, PP did not fully differentiate morphologically until at least this time when antigen can be handled in an efficient manner.