Maturation of the humoral immune response in mice

In spite of the prenatal appearance of immunoglobulin-bearing lymphocytes and theta-positive lymphocytes in the spleens of Swiss-L mice, these mice are not able to produce detectable levels of humoral antibodies in response to antigen until after 1 wk of age. Adult levels of response are not achieved until 4-8 wk of age. In the presence of bacterial lipopolysaccharides, which can substitute for or enhance T-cell function, the B cells from young Swiss-L mice were found to be indistinguishable in function from adult B cells, both with respect to the numbers of plaque-forming cells (PFC) produced in vitro in response to antigen and with respect to the kinetics of PFC induction. The spleen cells from young Swiss-L mice are significantly less sensitive than adult spleen cells, however, to stimulation by the T cell mitogens, concanavalin A (Con A) and phytohemagglutinin (PHA). Very few Con A-responsive cells could be detected at birth but the numbers increased sharply with age until 3 wk after birth. On the other hand, PHA-responsive cells could not be detected in the spleen until about 3 wk of age. The latter cells were found to respond also to Con A, but at a lower dose (1 microg/ml) than that required for the bulk of the Con A-responsive cells (3 microg/ml). The cells that respond both to PHA and to Con A appear in the spleen at about the time that Swiss-L mice acquire the ability to produce humoral antibodies, and these cells can be depleted from the spleen by the in vivo administration of antithymocyte serum. The development of humoral immune responses in these mice therefore appears to be correlated with the appearance of recirculating T lymphocytes that are responsive both to PHA and to Con A.

Characterization of splenic lymphoid cells in fetal and newborn mice

In order to clarify the cellular events that precede the onset of immunological competence in the mouse, we have characterized and quantitated the lymphoid cells of the spleen as a function of age. Our results show that T cells and B cells both appeared in the spleens of Swiss-L mice as early as the 15th-16th day of gestation. Antigen-binding cells specific for each of three different antigens were also first detected during this same 24 h interval. The B cells and three varieties of antigen-binding cells increased in number rapidly and in parallel until about 1 wk after birth. The T cells, which were more numerous than B cells at first, increased in number somewhat more slowly. Coincident with the onset of response to antigen, there was a further increase in B cell numbers and a decrease in the T cell to B cell ratio. The capacity to respond to antigen by cellular proliferation and synthesis of antibody did not arise until about 2 wk after birth although there were no quantitative changes in the total numbers of T cells, B cells, and antigen-binding cells between 1 and 2 wk of age. Some qualitative change, such as the functional maturation of an antigen-reactive cell, may be required during this interval for the onset of this immunological response. Although the numbers of antigen-binding cells present in fetuses and young animals were smaller than in adults, we have as yet been unable to detect any restriction in the variety of specificities that can be expressed in fetuses, either in the kinds of antigens bound or in the range of avidities with which a single antigen is bound.

Chemical dissection of mammalian spermatozoa

Spermatozoa from several mammalian species have been dissected by chemical methods to yield free heads, tails with attached midpieces, and tails from which the mitochondrial components of the midpiece were removed. Mouse and rat spermatozoa were cleaved by brief treatment with trypsin to yield free heads and tails, while human, guinea pig, and rabbit spermatozoa were cleaved by trypsin only after incubation with 2-mercaptoethanol or dithiothreitol. Spermatozoa were also cleaved at the junction of the head and the tail by treatment with acid and base. Mitochondria were removed from intact spermatozoa or isolated tails by mechanical shear after treatment with 2-mercaptoethanol or dithiothreitol. The dissected components of spermatozoa were fractionated with good yield and high purity by density gradient centrifugation. Ultrastructural analysis indicates that proteolytic cleavage to yield separated heads and tails occurs at a specific location in the neck of the spermatozoon, leaving the basal plate attached to the head of the cell. In contrast, after acid cleavage the basal plate remains with the midpiece. Proteolytic treatment has no apparent effect on any other spermatozoan structures, whereas acid or base treatment results in damage to the plasma membrane, the acrosome, and other structures. The specificity of the proteolytic cleavage suggests that a particular protein or group of proteins may be responsible for the linkage between the sperm head and tail.

Proteins specified by herpes simplex virus. VI. Viral proteins in the plasma membrane

Previous papers in the series have shown that the surface membranes of herpesvirus-infected cells acquire new immunological specificities and that purified infected cell membrane preparations, characterized by their physical properties rather than topology in the cell, contain new glycoproteins genetically determined by the virus. In this study, we prepared purified plasma membrane identified by its 5' nucleotidase, fucose, and reduced nicotinamide adenine dinucleotide-diaphorase content. Analysis of the membrane proteins and glycoproteins by electrophoresis in acrylamide gels indicated the following. (i) Purified plasma membranes from infected cells contained two sets of proteins, i.e., host proteins were present both before and after infection and viral proteins were present only after infection. (ii) After infection, no appreciable selective or nonselective loss of host proteins from membranes was demonstrable. However, no new host proteins were made. (iii) Electropherograms of plasma membrane proteins from infected cells indicated the presence of at least 12 virus-specific proteins ranging in molecular weight from 25 x 10(3) to 126 x 10(3) daltons. Of these, at least nine were glycosylated. Proteins and glycoproteins with similar electrophoretic mobilities but in somewhat different ratios were also present in preparations of highly purified virions.

Proteins specified by herpes simplex virus. V. Purification and structural proteins of the herpesvirion

We are reporting a procedure for the purification of herpes simplex enveloped nucleocapsids (virions), an evaluation of the purification procedure and the results of analyses of the virion proteins by high-resolution acrylamide gel electrophoresis. The data may be summarized as follows. (i) The procedure for the purification of virions consists of careful extraction of cytoplasm to prevent nuclear breakage, separation of enveloped nucleocapsids from soluble proteins and membrane vesicles by rate zonal centrifugation of cytoplasmic extracts through dextran 10 gradients, treatment with urea to dissociate virus-debris aggregates, and, lastly, separation of virions from naked nucleocapsids and free membranes by isopycnic flotation in discontinuous sucrose gradients. (ii) Purity was evaluated in three ways, i.e., electron microscopic examination, analysis of purified virions produced in cells labeled with amino acids before infection, and analysis of purified virions from artificial mixtures of infected and labeled, uninfected cells. The extent of purification was 120-to 200-fold with respect to host proteins. Residual contaminants were identified as host and viral constituents of membrane vesicles. Residual host proteins are very likely contaminants and not structural components of the virion. (iii) Analyses by staining and autoradiography of structural proteins of purified virions in 6, 7, 8.5, 9, and 14% acrylamide gels revealed 24 bands of proteins and glycoproteins made and labeled after infection. Co-electrophoresis of viral proteins with six known standards ranging from 25,700 to 220,000 daltons in molecular weight in 6, 7, 8.5, and 9% acrylamide gels indicate that viral proteins range from 25,000 to 275,000 daltons. The sum of the molecular weights of viral proteins is 2,580,000 daltons. Assuming that messenger transcription is asymmetric and noncomplementary, this corresponds to 47% of the genetic information of the virus. (iv) The nonionic detergent NP-40 removes from purified virions some nonglycosylated proteins and a large fraction of the glycosylated proteins. It leaves behind traces of the envelope visible in the electron microscope as well as some glycoproteins thought to be in the envelope.

Size and composition of Marek's disease virus deoxyribonucleic acid

Deoxyribonucleic acid (DNA) extracted from purified nucleocapsids of Marek's disease herpesvirus (MDV) was cosedimented with T4 and with herpes simplex virus (HSV) DNA in neutral sucrose density gradients and with T4 DNA in alkaline sucrose density gradients. These experiments indicated that the intact MDV DNA had a sedimentation constant of 56S corresponding to a molecular weight of 1.2 x 10(8) daltons. In the alkaline gradients, the largest and most prominent band contains a DNA sedimenting at 70S corresponding to 6.0 x 10(7) daltons in molecular weight. The DNA is therefore double-stranded and not cross-linked. Isopycnic sedimentation of the MDV DNA molecules with SPO1, Micrococcus lysodeikticus, and HSV DNA gave a density of 1.705 g/cm(3) corresponding to 46 guanine plus cytosine moles per cent. Lastly, in hybridization tests the DNA hybridized with RNA of infected cells but not with that of uninfected cells supporting the conclusion that it is viral.

Herpesvirus antigens on cell membranes detected by centrifugation of membrane-antibody complexes

Herpesviruses specify new glycoproteins that bind to cell membranes and also appear in the envelope of the virion. Incubation of purified smooth membranes from infected cells with antiviral antibody results in an increase in the density of the membranes as determined by flotation in sucrose density gradients. The magnitude of this increase depends on the amount of antibody used; densities as high as 1.16 grams per cubic centimeter have been obtained (the density of the untreated membranes is 1.08 grams per cubic centimeter). Antiviral antibody does not increase the density of uninfected cell membranes nor do saline or normal rabbit serum change the densities of infected or uninfected cell mnembranes. Viral antigens-presumably the glycoproteins specified by the virus-are probably on the surface of the infected cell membranes and bind to them strongly enough to withstand the hydrodynamic forces applied to them in the sucrose gradient.

Proteins specified by herpes simplex virus, IV. Site of glycosylation and accumulation of viral membrane proteins

The membrane glycoproteins specified by herpes simplex virus are synthesized concurrently with structural viral proteins and accumulate in the cytoplasm and in the membranes lining it. Analyses of free and membranebound polyribosomes, the cytoplasmic pool of soluble proteins, and purified smooth membranes showed that viral membrane proteins bind to membranes soon after synthesis and become glycosylated in situ.

Proteins specified by herpes simplex virus. 3. Viruses differing in their effects on the social behavior of infected cells specify different membrane glycoproteins

We examined the electrophoretic properties of the proteins and glycoproteins in the smooth membranes and virions purified from cells infected with herpes simplex virus strains differing with respect to their effects on the interaction of cells among themselves. The data show the following: (1) The glycoproteins in virions and binding to membranes share common features but vary quantitatively and qualitatively depending on the virus strain. (2) The binding to smooth membranes is ordered and not random. (3) Differences in the glycosylation of membrane proteins in African green monkey (VERO) and human (HEp-2) cells indicate that glycosylation is at least in part determined by the host.

Proteins spcified by herpes simplex virus. II. Viral glycoprotins associated with cellular membranes

Membranes prepared from HEp-2 cells infected with herpes simplex virus and free from soluble proteins, virus, ribosomes, and other cellular constituents were solubilized and subjected to electrophoresis on acrylamide gels. The electropherograms showed the following. (i) The synthesis of host proteins and glycoproteins ceases after infection. However, the spectrum of host proteins in membranes remains unaltered. (ii) Between 4 and 22 hr postinfection, at least four glycoproteins are synthesized and bound to the smooth cytoplasmic membranes. On electrophoresis, these glycoproteins form two major and two minor bands in the gel and migrate with proteins ranging from 50,000 to 100,000 daltons in molecular weight. (iii) The same glycoproteins are present in all membranes fractionated by density and in partially purified virus. The implications of the data are discussed.

Marek's disease herpes virus: a cytomegalovirus

The DNA of herpes viruses associated with Marek's disease of fowl contains 56-57 moles of guanine and cytosine per 100. The composition of its DNA and lack of infectiousness of cell-free preparations suggest that the herpes virus associated with Marek's disease belongs to the herpes virus group B which contains predominantly cytomegaloviruses.