Genetic studies of an acardiac monster: evidence of polar body twinning in man.

Two maternally derived chromosome sets and both maternal histocompatibility antigen haplotypes were identified in the tissues of a malformed triploid acardiac twin that developed within the same chorion as its normal twin. These findings indicate that the twins arose as a result of independent fertilizations, by two different spermatozoa, of a normal haploid ovum and its diploid first-meiotic-division polar body.

First Report of a New Potyvirus, Tricyrtis virus Y, and Lily virus X, a Potexvirus, in Tricyrtis formosana in the United States.

Tricyrtis formosana (toad lily) is an herbaceous perennial in the family Liliaceae. Native to Asia, T. formosana is now used in the United States as an ornamental border plant in woodland and shade gardens. A T. formosana var. stolonifera plant showing chlorosis and mild mosaic symptoms obtained from a commercial grower in Columbia County, Oregon tested positive for potyvirus by ELISA using our genus Potyvirus broad spectrum reacting PTY-1 Mab (3). Electron microscopic examination of negatively stained leaf-dip preparations from symptomatic leaves showed a mixture of two sizes of flexuous rod-shaped particles, approximately 700 nm long (resembling potyviruses) and 470 nm long (resembling potexviruses). Total RNA extracts from symptomatic leaves were used in reverse transcription (RT)-PCR assays with potyvirus- or potexvirus-specific primers. The degenerate primers for the genus Potyvirus (2) direct the amplification of approximately 1,600-bp fragments from the 3' terminus of most potyviruses. Overlapping potexvirus cDNA clones were generated using degenerate genus Potexvirus replicase primers, and later, virus-specific primers in 3' RACE (4). The RT-PCR amplified fragments were cloned and sequenced. Analysis of the 1,688 nt potyvirus sequence (GenBank Accession No. AY864850) using BLAST showed highest identity with members of the Bean common mosaic virus (BCMV) subgroup of potyviruses. Pairwise amino acid comparisons of the CP region of the new potyvirus showed 78% identity to strains of Bean common mosaic necrosis virus, 77% identity with Soybean mosaic virus and Ceratobium mosaic virus, 72 to 76% identity to strains of BCMV, and only 50 to 64% identity with 54 other potyviruses. Additionally, similar pairwise analysis of the CP nucleotide sequence and 3'NCR of the new potyvirus generally revealed the same identity trend as described for the CP amino acid sequences, albeit with the highest nucleotide identities at less than 73% for CP and less than 66% for the 3'NCR. These results suggest that this virus is a new species in the genus Potyvirus (1), which we have tentatively named Tricyrtis virus Y (TrVY). BLAST analysis of the 3' terminal 3,010 nt potexvirus sequence (GenBank Accession No. AY864849) showed 89% nucleotide identity with Lily virus X (LVX). Pairwise amino acid comparisons of the putative gene products revealed 98, 95, 94 and 99% identity with LVX TGBp1, TGBp2, TGBp3-like, and CP, respectively, and 97% identity with the 108 nt 3'NCR. Homology with other members of the genus Potexvirus was less than 50% for these corresponding genes and gene products. ELISA and RT-PCR analysis for these two viruses in toad lily plants obtained from a grower in Illinois also revealed the presence of TrVY in three of seven cultivars and LVX coinfecting only one of the plants. The standard propagation method for T. formosana is plant division, which along with mechanical contact, provides efficient means for spread of both viruses. To our knowledge, this is the first description of this potyvirus and the first report of any potyvirus in T. formosana. LVX has been reported in Lilium formosanum, but to our knowledge, this is also the first report of LVX in T. formosana. References: (1) P. H. Berger et al. Potyviridae. Page 819 in: Virus Taxonomy: 8th Rep. ICTV, 2005. (2) M. A. Guaragna et al. Acta. Hortic. 722:209, 2006. (3) R. L. Jordan and J. Hammond. J. Gen. Virol. 72:1531, 1991. (4) C. J. Maroon-Lango et al. Arch. Virol. 150:1187, 2005.

Effect of pulsed high frequency electromagnetic radiation on embryonic mouse palate in vitro.

Palatal shelves from 14-day-old embryonic mice were exposed to a 27.12 MHz pulsed non-ionizing radiofrequency (Diapulse) for 20 min followed by 24-hour organ culture in nutrient agar. Diapulse-treated palatal shelves showed induction of cartilage within the mesenchymal compartment and loss of the overlying epithelium in contrast to controls which were free of cartilage. The results are thought to be independent of thermal changes and may be due to calcium flux within the tissue.

Host Range and Characterization of Sunflower mosaic virus.

ABSTRACT Sunflower mosaic is caused by a putative member of the family Potyviridae. Sunflower mosaic virus (SuMV) was characterized in terms of host range, physical and biological characteristics, and partial nucleotide and amino acid sequence. Cells infected with SuMV had cytoplasmic inclusion bodies typical of potyviruses. Of 74 genera tested, only species in Helianthus, Sanvitalia, and Zinnia, all Asteraceae, were systemic hosts. Commercial sunflower hybrids from the United States, Europe, and South Africa were all equally susceptible. The mean length of purified particles is approximately 723 nm. The virus was transmitted by Myzus persicae and Capitphorus elaegni, and also was seedborne in at least one sunflower cultivar. Indirect enzyme-linked immunosorbent assay tests with a broad-spectrum potyvirus monoclonal antibody were strongly positive. SuMV-specific polyclonal antisera recognized SuMV and, to a lesser extent, Tobacco etch virus (TEV). When tested against a panel of 31 potyvirus-differentiating monoclonal antibodies, SuMV was distinct from any potyvirus previously tested. SuMV shared four epitopes with TEV, but had a reaction profile more similar to Tulip breaking virus (TBV). SuMV did not possess epitopes unique only to TBV. The predicted coat protein had a molecular weight of 30.5 kDa. The 3' end of the virus genome was cloned and sequenced. Phylogenetic analysis of the coat protein amino acid sequence revealed that SuMV is a distinct species within the family Potyviridae, most closely related to TEV.

First Report of Bean yellow mosaic virus (Pea Mosaic Strain) in Verbena × hybrida.

Verbena × hybrida is an ornamental annual used in rock gardens as an edging plant and hanging baskets. It comes in a variety of colors and grows approximately 1.5 to 2.5 cm (6 to 10 inches) high. In the spring of 2002, verbena cv. Lavender Shades plants from California showing leaf mosaic symptoms tested positive for potyvirus using an antigen-coated plate enzyme-linked immunosorbent assay with our genus Potyvirus broad spectrum reacting PTY-1 monoclonal as the detecting antibody (3). The virus was transmitted mechanically to Nicotiana benthamiana by sap inoculation from infected verbena plants. Infected tobacco showed systemic mild mosaic symptoms. Total RNA extractions from infected verbena and tobacco leaves were used in reverse transcription-polymerase chain reaction (RT-PCR) assays with generic potyvirus-specific primers that amplify highly conserved 700-bp or 1,600-bp fragments from the 3' terminus of most potyviruses. This region includes the 3' noncoding region (3'NCR) and the potyviral coat protein (CP). The PCR-amplified fragments were cloned by using standard TA cloning procedures and sequenced using dye-terminator chemistry. The cloned nucleotide and putative coat protein amino acid sequences from the infected verbena and tobacco plants were compared with the corresponding regions of other potyviruses. Amino acid comparison of the CP region of the verbena po-tyvirus showed 95 to 96% identity to four pea mosaic strains (PMV) of Bean yellow mosaic virus (BYMV), 85 to 89% identity to 20 other strains of BYMV, 74 to 76% identity with six strains of Clover yellow vein virus (CYVV), and only 50 to 64% identity with 28 other potyviruses. Pairwise comparisons among and between the CP sequences of PMV, BYMV, CYVV, and other potyviruses revealed identities of 92 to 99% for BYMV∷ BYMV, PMV∷PMV, and CYVV∷CYVV; 84 to 89% for BYMV∷ PMV, 69 to 78% for BYMV∷CYVV and PMV∷CYVV, and 50 to 64% for all other potyvirus combinations. Additionally, similar pairwise analysis of the 3'NCR of the verbena potyvirus revealed 98 to 99% identity to PMV strains, 81 to 94% to other BYMVs, 68 to 75% to CYVVs, and 52 to 64% with other potyviruses. Other 3'NCR pairwise comparisons generally revealed the same identity trend as described for the CP. Further serological analysis with our panel of BYMV-specific, BYMV-subgroup, and potyvirus cross-reactive monoclonal antibodies (3) confirmed the designation of the verbena potyvirus isolate as a pea mosaic strain of BYMV. To our knowledge this is the first confirmed report of BYMV-pea mosaic strain in Verbena (1,2). References: (1) Agdia, Inc. Positive Ornamental Plant Samples. Agdia On-line Publication, 2003. (2) A. A. Brunt et al. Verbena hybrida. Plant Viruses Online: Descriptions and Lists from the VIDE Database. Version 20. On-line publication, August 1996. (3) R. L. Jordan, and J. Hammond. J. Gen. Virol. 72:1531, 1991.

Characteristics of a Potyvirus of the Bean Yellow Mosaic Virus Subgroup in Sesbania speciosa Germ Plasm.

A plant of Sesbania speciosa with leaf mosaic and distortion symptoms was identified in a germ plasm regeneration plot at Griffin, Georgia. The Sesbania virus produced mild or moderate mosaic symptoms on Glycine max cvs. Bragg and Tracy M, Lupinus albus, Nicotiana benthamiana, Pisum sativum cv. Perfected Wales, Phaseolus vulgaris cvs. Black Turtle, Bountiful, and Pinto, and did not infect N. tabacum. Bean yellow mosaic potyvirus (BYMV) and pea mosaic potyvirus (PMV) do not infect Perfected Wales pea and they produce mosaic, distortion, and necrosis on white lupine. The PMV strain tested produced much more severe symptoms on the three green beans, with top necrosis on Pinto. BYMV produced local latent infection of N. tabacum and BYMV and PMV produced mosaic with distortion on N. benthamiana. The Sesbania virus was seed-transmitted at a low rate in S. speciosa. Indirect-enzyme-linked immunosorbent assay tests with a general potyvirus monoclonal antibody and BYMV and white lupine mosaic virus (WLMV) polyclonal antisera were strongly positive. Tests of the Sesbania virus against a monoclonal antibody panel suggests that it is not BYMV or any of the previously described subgroup members, but is a member of the BYMV subgroup. This is the first report of a seedborne BYMV-like virus of Sesbania spp.

Hippocampal commissure defects in crosses of four inbred mouse strains with absent corpus callosum.

It is known that four common inbred mouse strains show defects of the forebrain commissures. The BALB/cJ strain has a low frequency of abnormally small corpus callosum, whereas the 129 strains have many animals with deficient corpus callosum. The I/LnJ and BTBR T+ tf/J strains never have a corpus callosum, whereas half of I/LnJ and almost all BTBR show severely reduced size of the hippocampal commissure. Certain F1 hybrid crosses among these strains are known to be less severely abnormal than the inbred parents, suggesting that the parent strains have different genetic causes of commissure defects. In this study, all hybrid crosses among the four strains were investigated. The BTBR × I/Ln hybrid expressed almost no defects of the hippocampal commissure, unlike its inbred parent strains. Numerous three-way crosses among the four strains yielded many mice with no corpus callosum and severely reduced hippocampal commissure, which shows that the phenotypic defect can result from several different combinations of genetic alleles. The F2 and F3 hybrid crosses of BTBR and I/LnJ had almost 100% absence of the corpus callosum but about 50% frequency of deficient hippocampal commissure. The four-way hybrid cross among all four abnormal strains involved highly fertile parents and yielded a very wide phenotypic range of defects from almost no hippocampal commissure to totally normal forebrain commissures. The F2 and F3 crosses as well as the four-way cross provide excellent material for studies of genetic linkage and behavioral consequences of commissure defects.

Two unique US isolates of Pepino mosaic virus from a limited source of pooled tomato tissue are distinct from a third (European-like) US isolate.

Three strains of Pepino mosaic virus (PepMV) found in the US have been cloned and sequenced by RT-PCR using total RNA from infected tissue as template, and degenerate potexvirus- and PepMV species- and isolate-specific primers. Despite limited source material, the complete nucleotide sequences (6413 and 6410 nts, respectively) of two isolates, PepMV-US1 and PepMV-US2, were obtained and analyzed using total RNA from less than 0.2 g of a pooled infected tomato leaf sample from Arizona. Sequence of the 3'-end of the third isolate from infected fresh tomato fruits from Maryland (PepMV-US3) was also determined. The genome organizations of PepMV-US1 and US2 were typical of the genus Potexvirus, with the following reading frame order: ORF 1, encoding a putative replicase; ORFs 2-4, triple gene block proteins (TGBp) 1-3; and ORF 5, coat protein (CP). Gene-for-gene comparison between PepMV-US1 and US2 revealed the following amino acid identities: 91% in replicase, 89% in TGBp1, 92% in TGBp2, 85% in TGBp3, and 93% in the CP; with an overall nucleotide identity of 86%. Nucleotide sequence comparisons between US1 and US2 and the European isolates showed only 79-82% identity, whereas the identity among the European isolates was over 99%. Sequence comparisons and phylogenetic analysis indicate that PepMV-US1 and US2 are distinctly different from the European isolates, while the CP of PepMV-US3 is nearly identical to the European isolates. The results presented also suggest that TGBp1 and TGBp3 are more suitable than either the replicase or coat protein gene products for discriminating PepMV isolates.

Drug-induced limb dysplasias in fetal rabbits.

Pregnant New Zealand White rabbits were treated on gestation day 12 with 19.2 mg/kg methotrexate (MTX), 750 mg/kg hydroxyurea (HU), or 1,500 mg/kg acetazolamide. Rabbits were killed either 2-32 hours posttreatment for histological analysis of embryos or at day 29 for gross and skeletal examination of fetuses. tmtx produced cleft palate, hydrocephalus, and fore- and hindlimb reduction defects. Histological analysis revealed pyknosis and edema in mesenchymal tissues at four to eight hours following treatment. The apical ectodermal ridges (AER) of treated embryos permanently lost their characteristic pseudostratified organization. By 32 hours the limb buds had regained their normal appearance except for the AER. HU affected all fetuses with skull and facial anomalies as well as severe reduction deformities of all limbs. Histologically HU-treated embryos had numerous, basophilic, intercellular granules (presumably cell debris) which appeared within two to four hours in the limb bud mesenchyme, neural tube, and dorsal root ganglion. The architecture of the AER was unchanged. Acetazolamide produced bilateral retarded ossification or possible aplasia of the first metacarpal and talus in nearly 80% of fetuses. Microscopic examination disclosed no apparent alterations in limb-bud morphology. Methyl green-pyronin Y staining called attention to green intracellular droplets within the endoderm of the trachea and bronchi at two hours posttreatment. It was concluded that the three drugs do not produce limb dysplasias by a common teratogenic mechanism.

Embryotoxicity of the folate antagonist methotrexate in rats and rabbits.

The prenatal effects of methotrexate (MTX) in rats and rabbits were assessed. It was found highly embryotoxic in postimplantation rat embryos; 0.3 mg/kg ip or less caused nearly total embryolethality with slight teratogenicity. Rabbit embryos were far more resistant to small doses of MTX than rats, but 19.2 mg/kg iv, when given during days 10 to 15 of gestation, produced little death and a constant spectrum of malformation in a high percentage of offspring. Cleft palate, skull defects, and severe fore- and hindlimb dysplasias, occurred with a high degree of regularity and were strongly dose and developmental-stage specific.

Identification of C3b as the major serum protein that stimulates prostaglandin and thromboxane synthesis by macrophages.

We have previously reported that heterologous, homologous and autologous sera, all stimulated rabbit alveolar macrophages to synthesize prostaglandins (PG). Gel permeation chromatography of serum showed multiple fractions possessing this stimulatory activity, with the major one at 150-160K daltons. In the present study, we have shown that: (a) Fresh rabbit serum stimulated PG release by macrophages. (b) Serum depleted of C3 and C5 lost its stimulatory activity. (c) Trypsinized serum, sera activated by aggregated IgG and zymosan, partially purified C3, C5 and the C3, C5 preparation or purified C3 activated by zymosan, all stimulated PG release by macrophages with the following order of potency: activated C3, C5 = activated C3 = zymosan-activated serum greater than trypsinized serum = aggregated IgG-activated serum greater than partially purified C3, C5 = serum. PGE2 was the predominant PG synthesized by stimulated macrophages. However, thromboxane (TX) production seemed to be more selectively enhanced i.e., increase in TX production was more pronounced than the increase in PGE release. To further identify the active complement component, we blocked the C3b receptor (C3 b R) by preincubating macrophages with anti-C3bR, and showed that subsequent treatment with activated C3 and C5 failed to elicit any PG release. This pretreatment with anti-C3bR had no inhibitory effect on subsequent zymosan stimulation of PG release. Thus we concluded that C3b was the major serum protein that stimulates PG synthesis by macrophages.

Immunological characterization of in vitro forms of homoserine dehydrogenase from carrot suspension cultures.

Multiple forms of homoserine dehydrogenase (HSDH) from carrot (Daucus carota L.) have been identified. One form of HSDH (T-form) has a relative molecular weight of 240,000 and is strongly inhibited by threonine. Another form (K-form) has a relative molecular weight of 180,000 and is insensitive to inhibition by threonine. The interconversion of these two forms is dependent upon the presence or absence of threonine and potassium. Polyacrylamide electrophoretic gels stained for HSDH activity and protein, paralleled with Western blot analysis, verified the interconversion of the T- and K-forms in 5 millimolar threonine and 100 millimolar potassium, respectively. Carrot HSDH also aggregates to form higher molecular weight complexes of 240,000 up to 720,000 M(r.) Polyclonal antibody from mouse was raised against the T-form (240,000 M(r)) of carrot HSDH. Specificity of the mouse antisera to carrot HSDH was verified by immunoprecipitation and Western blot analysis. The T-form, K-form, and all of the higher molecular aggregates of carrot HSDH cross-reacted with the anti-HSDH antiserum. The antiserum also cross-reacted with soybean HSDH, but did not cross-react with either of the two HSDH forms found in Escherichia coli. A model for the in vivo regulation of threonine biosynthesis in the chloroplast is presented. The model is based on the interconversion of the HSDH forms by potassium and threonine.

Rabbit lymphocyte factors modulate prostaglandin biosynthesis in alveolar macrophages.

We have previously shown that alveolar macrophages from BCG-infected rabbits release less prostaglandins (PG) and arachidonic acid than normal resident macrophages. In order to investigate the possible role of lymphocytes in modulating PG secretory activity of macrophages, we added the supernatant of spleen lymphocyte culture to alveolar macrophages prelabelled with [14C] arachidonic acid, and subsequently quantitated the release of PGs and arachidonic acid by macrophages. It was found that lymphocytes stimulated by phytohaemagglutinin (PHA) released soluble factors which inhibited arachidonic acid release and PG synthesis by macrophages. This inhibition was not seen with either supernatant of lymphocytes cultured without PHA, or when PHA was added at the end of lymphocyte incubation. The inhibitor factors were pronase-sensitive and exhibited molecular weight heterogeneity. Production of these could be enhanced by indomethacin treatment. These lymphokines might play a regulatory role in the suppression of macrophage PG synthesis in cell-mediated immunity.

Diversity of citrus tristeza virus isolates indicated by dsRNA analysis.

One major dsRNA of molecular weight (MW) 13.3 X 10(6) and two others (MW 1.9 X 10(6) and 0.8 X 10(6] were routinely detected by polyacrylamide gel electrophoresis in extracts from sweet orange (Citrus sinensis) or citron (Citrus medica) infected with each of 66 isolates of citrus tristeza virus (CTV). Several additional dsRNA were also commonly detected, usually as weakly stained bands in reproducible positions in gels, but some were very prominent, e.g., a dsRNA of MW 1.7 X 10(6) associated with a seedling yellows isolate (sy-1). No dsRNA was detected in equivalent extracts from noninoculated sweet orange and citron. End-labeled [32P] probes were made from purified full-length viral RNA or polyacrylamide gel-purified full-length dsRNA of a nonseedling yellows (nsy-1) and a seedling yellows (sy-1) isolate of CTV. Each of the four probes was able to hybridize to all major and most minor dsRNAs of both isolates in composite polyacrylamide/agrarose gels, including the 1.7 X 10(6) dsRNA specific to the seedling yellows isolate, and could readily detect CTV nucleic acid sequences in extracts from bark of infected sweet orange plants spotted onto nitrocellulose membranes. One dsRNA (MW 0.5 X 10(6] was very prominent in some isolates and much less so, or undetectable, in other isolates and 66 isolates have been screened for the presence of this dsRNA. There was a strong correlation between inability to detect the 0.5 X 10(6) dsRNA and the designation of an isolate as neither a seedling yellows type nor a stem pitting isolate of grapefruit; these properties were typical for isolates of CTV from southern California.

Identification of a unique isoform of 1-aminocyclopropane-1-carboxylic acid synthase by monoclonal antibody.

1-Aminocyclopropane-1-carboxylic acid (ACC) synthase (EC 4.4.1.14) is a key enzyme regulating ethylene biosynthesis in higher plants. A monoclonal antibody (mAb T20C) that immunoprecipitates the ACC synthase activity from tomato pericarp tissue extracts revealed that mAb T20C immunodecorates an approximately 67-kDa polypeptide. On isoelectric focusing gels, ACC synthase activity in cell-free preparations was resolved into three distinct activity peaks with pI values 5.3, 7, and 9. mAb T20C specifically recognized the pI 7 form of the enzyme on electrophoretic transfer (Western) blots. When analyzed by sodium dodecyl sulfate gel electrophoresis under reducing conditions, the eluted pI 7 form was confirmed to migrate as a polypeptide of 67 kDa. The 67-kDa pI 7 isoform is a previously undescribed form of ACC synthase.

Immunochemical and biological properties of a mouse monoclonal antibody reactive to prunus necrotic ringspot ilarvirus.

A monoclonal antibody reacting with prunus necrotic ringspot ilarvirus was tested in immunochemical studies, neutralization of infectivity assays, and by immuno-electron microscopy. The antibody was able to detect the 27,000 Mr coat protein of prunus necrotic ringspot ilarvirus in western blots and also detected all polypeptide fragments generated after incubation of whole virus with proteolytic enzymes. In neutralization of infectivity studies, the antibody blocked virus infectivity, although it did not precipitate the antigen in agar gel Ouchterlony double diffusion tests. Immuno-electron microscopy confirmed that the antibody coats virions but does not cause clumping. The antibody may be a useful tool for investigating coat protein-dependent initiation of ilarvirus infection.

Serum and plasma stimulate prostaglandin production by alveolar macrophages.

Fetal bovine serum (FBS) stimulated rabbit alveolar macrophages to synthesize prostaglandins (PG) and release lysosomal enzymes. This stimulatory action was not entirely due to the effect of foreign protein in FBS, since rabbit serum and plasma, both homologous and autologous, also induced release of PGs and lysosomal enzymes. Rabbit serum and plasma are less effective than FBS as a stimulus for PG release, with rabbit serum being more potent than plasma at the same concentration. Bovine serum albumin elicited a dose-dependent increase of arachidonic acid release by macrophages, but not of PG production. Hence, the fatty acid "trapping" effect of albumin in serum and plasma is not responsible for the PG stimulation. The PG stimulating factors were stable at 56 degrees C for 30 min., but lost half the activity after heating at 100 degrees C for 10 min. Gel permeation chromatography of FBS showed several peaks of PG stimulating and arachidonic acid releasing activity. The molecular weight of the major one (150,000 daltons) is similar to that of immunoglobulin G. Rabbit IgG, when added to the macrophage culture, stimulated release of arachidonic acid and PGs. However, the major stimulatory effect in serum or plasma is not all due to IgG, since removal of IgG by a Protein A-agarose column did not remove the stimulatory effect of FBS and rabbit serum. The possibility of other factors, such as complement fragments, is discussed.

Detection of channel catfish virus DNA in latently infected catfish.

Channel catfish virus (CCV) disease is an acute haemorrhagic disease in juvenile channel catfish (Ictalurus punctatus). While fish that survive primary CCV infection are suspected of being carriers of CCV, little is known concerning CCV latency. In this report, fingerling catfish were infected with CCV by experimental immersion challenge. Infected fish displayed clinical signs of CCV disease, but 22% of infected fish survived the acute disease. At 140 days post-infection, PCR analysis detected CCV DNA in the blood, brain, intestines, kidney, liver and peripheral blood leukocytes of latently infected fish. Further analysis indicated the CCV genome may exist as circular or concatemeric DNA during virus latency. This study, employing an experimental model of CCV disease, confirms that CCV establishes a latent infection of channel catfish.

In vitro ozone exposure inhibits mitogen-induced lymphocyte proliferation and IL-2 production.

Human blood mononuclear cells were exposed to ozone in vitro and thereafter analyzed for competence in mitogen-induced proliferation as well as IL-1 and IL-2 production. Proliferative responses induced by phytohemagglutinin (PHA), concanavalin A (Con A), and pokeweed mitogen (PWM) were all depressed in lymphocytes exposed to an ozone concentration of 1 ppm for 4-6 h. The response to PWM was most sensitive to the ozone effect (38% suppression); responses to Con A and PHA were suppressed to a lesser extent, 23% and 18%, respectively, and were not significantly different from each other. PWM responses were affected at an ozone concentration as low as 0.1 ppm; however, no suppression of Con A-induced proliferation was seen below 0.18 ppm or of PHA-induced proliferation below 0.5 ppm. When lymphocytes and monocytes were exposed separately to ozone and then mixed back with control air-exposed monocytes or lymphocytes, both cell types appeared to be affected and the functional defects caused by the pollutant were additive. Monocyte IL-1 production induced by endotoxin was not affected by ozone exposure, while surface expression of HLA-DR on exposed monocytes was reduced by 40% 24 h after exposure. Moreover, lymphocytes exposed to ozone produced 46% less IL-2 while expressing similar surface density of IL-2 receptors. Taken together, these results show that exposure to ozone has distinct adverse effects on lymphocytes and monocytes, both of which are important in local immune defenses in the lung.