Amino acid sequence of the N-terminal sixty-nine residues of heavy chain derived from a homogeneous rabbit antibody

The sequence of the N-terminal 69 residues of heavy chain from a homogeneous rabbit antibody to type III pneumococcal polysaccharide was determined. The sequence is similar to that found in heavy chains of normal pooled rabbit immunoglobulins of the same allotype Aa1. Two regions of the homogeneous heavy chain (residues 35-46 and 62-69) are very similar to corresponding regions of heavy chains from rabbit Aa2 immunoglobulin, as well as from mouse, guinea-pig and human immunoglobulins. In contrast, residues 47-62 appear to be variable. Comparison in this section with another homogeneous anti-pneumococcal antibody (Strosberg et al., 1972) of related specificity and of the same allotype indicates sequence variation in at least three positions. An antibody to group C streptococcal carbohydrate of allotype Aa2 (Fleischman, 1971) differs by five amino acids in the same region of the heavy chain. Sequence variability between these three antibodies does not occur in homologous positions within this variable section. Allotype-related sequences could not be identified in section 34-65.

Dog homologue of human 2 -microglobulin

The amino-acid sequence of human beta(2)-microglobulin, a protein of 100 residues, is related to parts of the constant region of IgG heavy chain. The dog homologue of human beta(2)-microglobulin has now been isolated and its amino-acid sequence has been partially determined. The two proteins (human and dog beta(2)-microglobulins) are demonstrably different at only 6 or 7 of the 42 positions examined. Use of the dog should permit experimental investigation of the functional relationships of beta(2)-microglobulin to immunoglobulins and the immune system. beta(2)-Microglobulin has also been detected in serum from a chimpanzee. The gene for beta(2)-microglobulin may correspond to the end portion of an immunoglobulin heavy chain gene.

Homology and relatedness of amino acid interchanges in the variable region of kappa light chains from human immunoglobulins

We have devised a method for assessing the relatedness of amino acid interchanges in the variable regions of immunoglobulin polypeptide chains, in terms of the nature of the differences between trinucleotide codons. We have used it to construct a map of the average human κ chain showing the positions which (i) give the chain κ identity, (ii) give the chain subgroup identity within the κ type, (iii) give the chain identity within a subgroup, and (iv) are invariant. In order to determine the positions at which the interchanges are homologous, we have performed a second analysis using the assumption that functionally equivalent amino acids are identical.κ Identity was found throughout the amino-terminal half of the chain (positions 1–108, the variable region). Subgroup identity was not found beyond invariant Phe 98, but was very pronounced in the first 22 positions of the chain. κ and subgroup identity were evident within hypervariable regions (positions 27–35, 48–52, and 90–97), however. A high degree of functional homology was found in the 11 residues at the end of the variable region and at certain individual positions scattered throughout the variable region, but not in the hypervariable regions.The distribution of these different classes of positions might reflect the distribution of certain functions within the chains.

IgG heavy chain sub-classes in mixed cryoglobulins

IgG heavy chain sub-classes were assayed in thirteen mixed cryoglobulins. In eight the distribution of sub-classes in the cryoglobulin was different from that in the serum. In two the IgG component of the cryoglobulin consisted entirely of IgG3. A restricted distribution of heavy chain sub-classes in mixed cryoglobulins probably reflects the heavy chain specificities of the antiglobulin components.

Immunglobulin classes, subclasses and complexes of IgG rheumatoid factor in rheumatoid plasma cells

The different immunoglobulin classes, IgG subclasses and types of light chains in plasma cells of thirty-four rheumatoid synovial membranes were studied. In some of these membranes a particular Ig class or IgG subclass was selectively concentrated, indicating local production of antibodies. Large amounts of plasma cells containing IgG were detected in all tissues. In contrast, many synovial membranes contained only few plasma cells with free rheumatoid factor activity, shown by binding of aggregated IgG. However, after pepsin digestion of tissue sections, greatly increased numbers of plasma cells were able to bind IgG. Our results indicated that the majority of plasma cells of rheumatoid tissues contained rheumatoid factors, but these were mostly blocked, due to intracellular complexing of IgG rheumatoid factors.

Immunofluorescence studies on immunoglobulins in the lymphoid cells of human peripheral blood

Immunofluorescence was applied for the detection of intracellular immunoglobulins in human peripheral blood cells. The technique permitted the screening of large numbers of cells and the discrimination of two fluorochromes within each cell. In this way distribution patterns were obtained for the major immunoglobulin classes and for both light chain types. In contrast to the analogous bone marrow patterns there was no correlation with the distribution pattern of the immunoglobulins in the serum in the samples without paraproteinaemia. These results are compatible with the view that the bone marrow—but not the blood—is to be considered as a major source of the immunoglobulins in the serum. This hypothesis also implies that the initial phase of antibody production takes place in the peripheral lymphoid organs with a homing tendency of the immunoglobulin-producing cells in the bone marrow. The findings in paraproteinaemia support this view. Information about the quantitative contribution of the peripheral lymphoid organs is insufficient to draw definite conclusions.

It became furthermore apparent that there can exist an intracellular imbalance with regard to the heavy versus the light chain components of the immunoglobulin molecules. The result often is an H/L ratio in excess of unity.