Private and public antigens of the mouse H-2 system

Natural antibodies and cancer

The innate or natural immunity is the basis and key for all immune processes. Specific receptors on macrophages, dendrites, NK cells and natural antibodies producing B cells act as a first line defense and remove all 'foreign' and potentially harmful substances, that is, bacteria, viruses, cellular waste, modified molecules and, most importantly, cancer cells. Recognition and removal of transformed cells is a lifelong task of immune surveillance processes. Antibodies are hallmark components of this anti-cancer activity. To investigate their nature, specificity, and function, we used the human hybridoma technology for isolating antibodies from cancer patients. These were then tested with a panel of assays against cancer cell lines in vitro and in vivo. Interestingly, all the tumor-specific antibodies we found were germ-line coded and belonged nearly exclusively to the IgM class. Furthermore, they all bound to new carbohydrates on post-translationally modified cell surface receptors on malignant cells. So far no affinity maturated immunoglobulins detecting tumor-specific peptides were found. However, only the presentation of peptide motifs can create an immunological memory. In general malignant cells are detected at very early precursor stages and manifest tumors can be considered as exceptional events. In addition, malignant cells are neither infectious nor hide intracellularly like viruses and some bacteria. Therefore, it makes sense that anti-tumor immunity seems to be solely a part of the natural immunity and a memory is not needed and therefore not induced. This indicates that the tumor immunity seems to be restricted to innate immune mechanisms and the instruments used by nature, like natural antibodies, are obviously excellent therapeutics.

Tumors: too sweet to remember?

Immunity, based on a natural and an educated system, is responsible for recognition and elimination of infectious particles, cellular waste, modified self and transformed cells. This dual system guarantees that dangerous particles are removed immediately after appearance and that a memory with maturated weapons exists, if the organism is re-infected by the same particle. For malignant cells, however, the immune response seems to be restricted to innate immunity, because at least for the humoral response, all so far detected tumor-specific antibodies belong to the natural immunity. In this review we try to explain why malignant cells might be "too sweet" to induce a memory.

Natural antibodies and cancer

Immunity is not only responsible for recognition and elimination of infectious particles, but also for removal of cellular waste, modified self structures and transformed cells. Innate or natural immunity acts as a first line defense and is also the link to acquired immunity and memory. A striking phenomenon of immunity against malignant cells is that neither in animals nor in humans affinity-maturated tumor-specific IgG antibodies have been detected so far. All tumor-specific isolated antibodies were germ-line coded natural IgM antibodies. It's also a fact that these IgM's preferentially bind to carbohydrate epitopes on post-transcriptionally modified surface receptors and that they all induce a cancer-specific apoptosis, by triggering the intrinsic apoptotic pathway. From an evolutionary point of view, this makes sense because cancer cells are not infectious, so there is no need for memory. Natural IgMs bind to conservative structures because they are coded by a limited set of genes and they use apoptosis, the "clean" way of killing, to avoid inflammatory processes.

Major histocompatibility complex of the mole-rat. I. Serological and biochemical analysis

The mole-rat, Spalax ehrenbergi, is a complex subterranean rodent species whose habitat is restricted largely to the Middle East and North Africa. We typed over 50 mole-rats with mouse monoclonal and polyclonal antibodies specific for class I and class II major histocompatibility complex (Mhc) molecules. Some of these antibodies were produced against mouse Mhc molecules, others against Mhc molecules of other species. About 25% of the antibodies reacted with mole-rat lymphocytes in the cytotoxic test. Some of the serologically positive antibodies precipitated from a glycoprotein pool of mole-rat spleen cell molecules that corresponded in size with class I and class II molecules of other species. We conclude, therefore, that mole-rats, like other mammals, possess the Mhc which consists of class I and class II loci. We call this Mhc Spalax major histocompatibility (Smh) complex. The occurrence of a large number of different serotypes among the tested animals suggests that Smh loci are polymorphic. This Mhc polymorphism of the mole-rat contrasts with the monomorphism or oligomorphism of the Syrian hamster, a rodent with a similar ecology. Thus far no qualitative correlation could be found between Smh polymorphism and chromosome variation described in this superspecies.

Comparative Studies on S-Glycoproteins Purified from Different S-Genotypes in Self-Incompatible BRASSICA Species II. Immunological Specificities

Antisera were prepared by immunization of apparently purified S-glycoproteins; one from an S allele of Brassica campestris and two from S alleles of B. oleracea. Each antiserum was reactive not only with the homologous S-glycoprotein but also with the heterologous ones, i.e. with the S-glycoproteins of the other S alleles of the same locus. In double diffusion tests, a spur against the heterologous S-glycoproteins suggested heterogeneity of the glycoproteins. The heterogeneity appears to involve a component of the molecule in which the genotypic specificity of an S-glycoprotein resides, probably, for the recognition site. Some molecular components are common to all tested S-glycoproteins and in this respect are like the public antigens of the MHC locus of mammals. The common molecular components were recognized between the S-allele-specific glycoproteins within B. oleracea and also between them and those of B. campestris. No S-specific substances were detected in buffer soluble homogenates of style, ovary or anther. However, these homogenates contained substances that had structures similar to the corresponding common parts of the S-glycoproteins.

Further molecular complexities of H-2 K- and D-region antigens

The K and D regions of the H-2 gene complex are highly polymorphic and control cell-surface structures involved in the H-2 restriction of cytotoxic T lymphocytes. Originally it was assumed that each of these regions controlled only one type of antigenic molecule, H-2K and H-2D, respectively. The finding that the D region controls H-2L and H-2M, as well as H-2D, molecules suggests that the system of H-2 antigens is more complicated. We demonstrate here previously unknown H-2 molecules detected by anti-K- and D-region alloantisera in co-capping experiments. Three different types of molecule, distinct from Ia and Qa antigens, are distinguished in the products of the Ddx region, and two in the products of the Dk and Kd regions. Analysis of the antigenic heterogeneity of K- and D-region products may further understanding of the function of these regions in cell-mediated immunity.

Expression of foreign H-2-like antigens by a chemically-induced murine tumour (MCG4)

Alien H-2k-like antigens were found to be expressed by a methylcholanthrene induced tumour of BALB/c (H-2d) origin. H-2 specificities of the k haplotype were detected on this tumour by a variety of serological techniques, including 51Cr-release cytotoxicity, microradioassay and absorption. The antisera employed were conventional polyspecific alloantisera, typing sera with restricted specificty and monoclonal hybridoma-derived anti-H-2k antibodies. The tumour has a low expression of the private specificty 31, which characterizes Kd molecules, and does not seem to express the private specificities of Dd, Kk and Dk molecules. It appears to express predominantly alien H-2-like antigens which are very similar to but not identical with normal H-2k molecules.

Frequency distribution of histocompatibility-2 antigenic specificities in the Japanese wild mouse genetically remote from the European subspecies

Fifty-eight Japanese wild mice, Mus musculus molossinus, collected from twenty-eight localities were surveyed for twelve H-2 antigens using the haemagglutination method. Significantly higher frequencies of H-2.3 and H-2.5 specifities and relatively lower frequencies of the other public specificities were observed. This was confirmed by examining four specificities, H-2.3, 5, 13 and 23, in 370 mice. Quantitative absorption of the alloantisera by erythrocytes and spleen lymphocytes of molossinus mouse revealed definite absorption of H-2.3, 5 and 8 antigens, though their antigenic strength was apparently weaker than the controls, B10 congenic mice. Comparative assay of the strength of H-2.5 antigen in either homozygous and heterozygous conditions distinctly eliminated the possibility of gene-dose effect for the reduced strength of the public antigens in molossinus mouse. To explain this, divergence time between molossinus and domesticus was computed based on the allelic frequency data already reported on ten loci in both subspecies. It is roughly 1.5 x 10(6) years, which could allow for the occurrence of considerable genetic changes in many public antigens, except those conserved through selection.

The major histocompatibility complex of the mouse

Like physicists striving to develop a unified field theory, immunologists are attempting to bring order to the microcosmos of defense reactions. Indications are that one of the most important constants in this microcosmos is the major histocompatibility complex (MHC) of the species. A test of any interpretation of the MHC's role in immunity is how well it explains this system's polymorphism. One of the most crucial questions an MHC hypothesis must answer is: Why are there so many alleles at this complex?

The partial amino-acid sequence of an H-2K molecule

Eighteen of the NH2-terminal 27 amino acids of a murine H-2K molecule have been assigned. The approach used was to label murine splenocytes with a single radioactive amino acid, isolate the H-2K molecule by specific immunoprecipitation, electrophorese the dissolved precipitate on sodium dodecyl sulfate polyacrylamide gels, and subject the isolated H-2K peak to amino-acid analysis and automated sequencing.

Deoxyribonucleic acid synthesis induced with ultraviolet light in Brij 58-treated Bacillus subtilis spores germinated in the presence of chloramphenicol

The direct measurement of ultraviolet light-stimulated DNA synthesis in the permeable Bacillus subtilis cells was performed. Bacillus subtilis spores germinated in the presence of chloramphenicol were treated with Brij 58 and irradiated with ultraviolet light, and (3H)dTTP was incorporated into these cells by the DNA polymerase assay system. Characteristics of the incorporation were distinct from those into spores germinated in the absence of chloramphenicol and treated with Brij 58, in the respect that the former incorporation did not require ATP and only partially depended on the presence of all four deoxyribonucleoside triphosphates. The incorporation of (3H)dTTP into DNA was confirmed by CsCl density gradient centrifugation. A DNA polymerase I-deficient strain, JBl 49(59) had no (3H)sTTP incorporating activity induced by ultraviolet light irradiation when the germinated spores were treated with Brij 58. Analysis of alkaline sucrose gradient centrifugation revealed that fragmented DNA caused by ultraviolet light irradiation was rejoined to the size of DNA of non-irradiated cells by incubating irradiated cells in the DNA polymerase assay mixture containing NAD+. The results also suggested that a machinery of DNA repair probably pre-existed in the spore.

Host-gene control of C-type tumor virus-expression and tumorigenesis: relevance of studies in inbred mice to cancer in man and other species

C-type RNA viruses are tumorigenic in mice and other species. They are widespread and transmitted in an intimate relationship with host-cell genetic material. Tumorigenesis is no doubt a complex biological phenomenon, and involves both genetic and environmental factors. Among the genetic factors, single-locus determination is probably exceptional; yet, a number of genes are known in inbred mice and other species, including man, that can exert a major influence. Clearly, studies with inbred mice apply outside the murine model and justify generalizations on the etiology of cancer. The types of cancer observed in man are similar to those of inbred strains of mice, and their stochastic and often familial occurrences suggest that genetic factors play important roles in both man and mouse. A number of heritable disorders predipsose to tumorigenesis. Investigations of the relationship between various polymorphic phenotypes and human tumors should be intensified. For instance, a study of high-risk human-tumor groups could aid considerably not only in the recognition of etiological agents but also of underlying host-gene controlled mechanisms. Indeed epidemiological studies have already led to the identification of mutant genes that influence the incidence of human cancer. Such studies may be guided by findings in inbred strains of mice. There is good evidence in inbred mice that mutations in host chromosomes determine whether or not genes coding for RNA oncogene viral "functions" become expressed as cancer. Although an etiological role of C-type RNA virus has not yet been demonstrated in human cancer, studies of the interaction of viral and host-cell genomes in mice and other species, and the visualization of C-type virus in human tumors have provided good reasons for suspecting the presence in man of oncogenic genes (oncogenes) homologous to those of the C-type viral genomes, which are well studied in mice, hamsters, cats, rats, and chickens.