Maintenance of long-lived plasma cells and serological memory despite mature and memory B cell depletion during CD20 immunotherapy in mice

CD20 mAb-mediated B cell depletion is an effective treatment for B cell malignancies and some autoimmune diseases. However, the full effects of B cell depletion on natural, primary, and secondary Ab responses and the maintenance of Ag-specific serum Ig levels are largely unknown. The relationship between memory B cells, long-lived plasma cells, and long-lived humoral immunity also remains controversial. To address the roles of B cell subsets in the longevity of humoral responses, mature B cells were depleted in mice using CD20 mAb. Peritoneal B cell depletion reduced natural and Ag-induced IgM responses. Otherwise, CD20+ B cell depletion prevented humoral immune responses and class switching and depleted existing and adoptively transferred B cell memory. Nonetheless, B cell depletion did not affect serum Ig levels, Ag-specific Ab titers, or bone marrow Ab-secreting plasma cell numbers. Coblockade of LFA-1 and VLA-4 adhesion molecules temporarily depleted long-lived plasma cells from the bone marrow. CD20+ B cell depletion plus LFA-1/VLA-4 mAb treatment significantly prolonged Ag-specific plasma cell depletion from the bone marrow, with a significant decrease in Ag-specific serum IgG. Collectively, these results support previous claims that bone marrow plasma cells are intrinsically long-lived. Furthermore, these studies now demonstrate that mature and memory B cells are not required for maintaining bone marrow plasma cell numbers, but are required for repopulation of plasma cell-deficient bone marrow. Thereby, depleting mature and memory B cells does not have a dramatic negative effect on preexisting Ab levels.     

Maintenance of abiotic stress memory in plants: Lessons learned from heat acclimation

Plants acquire enhanced tolerance to intermittent abiotic stress by employing information obtained during prior exposure to an environmental disturbance, a process known as acclimation or defense priming. The capacity for stress memory is a critical feature in this process. The number of reports related to plant stress memory (PSM) has recently increased, but few studies have focused on the mechanisms that maintain PSM. Identifying the components involved in maintaining PSM is difficult due in part to the lack of clear criteria to recognize these components. In this review, based on what has been learned from genetic studies on heat acclimation memory, we propose criteria for identifying components of the regulatory networks that maintain PSM. We provide examples of the regulatory circuits formed by effectors and regulators of PSM. We also highlight strategies for assessing PSMs, update the progress in understanding the mechanisms of PSM maintenance, and provide perspectives for the further development of this exciting research field.

A review of the strategies and principles for assessing abiotic stress memory in plants, the roles of components that maintain stress memory, and the regulatory circuits they form.     

Maintenance and amplification of cell-associated immunological memory in in vivo culture system

By employing bovine serum albumin as antigen and the capsular polysaccharide of Klebsiella pneumoniae as adjuvant, maintenance and amplification of immunological memory were analyzed in an in vivo culture system in mice. For this purpose, the double cell transfer technique was employed to minimize the influence of regulatory factors on memory expression. Memory associated with primed cells is maintained at the original level during in vivo culture for at least a month in the absence of antigen. In contrast, memory is amplified more than 30 times during this period by stimulation with antigen. This secondary increase in memory does not require the action of adjuvant. Neither the residual primary antigen nor preformed primary antibody seems to play a significant role in the maintenance and amplification of memory of the primed cells. From these results it is probable that the enduring immunological memory in actively immunized mice is conveyed by long-lived memory cells, and additional antigenic stimulating on once-established memory cells serve to amplify (not simply to maintain) memory in a secondary fashion.     

Maintenance of a short-lived protein required for long-term memory involves cycles of transcription and local translation

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Biochemical and serological characteristics of Escherichia belonging to the serological group 01]

A circulation at the territory of the country of various biochemical and serological variants of escherichia belonging to serological group O1, isolated in acute intestinal diseases of children and adults, was revealed. Nonhomogeneousness of the partial composition of the O-antigen was demonstrated; K-antigens were determined; new H-antigens were described. Of the 10 serological types of escherichia there proved to prevail O1 : K? : Hp and O1 : K1 : Hp; in group and sporadic acute intestinal diseases there were for the first time isolated O1 : K1 : H34, O1 : K1 : H20, O1 : K1 : Hp, O1 : K51 : H7, and O1 : K? : H20.     

The serological responses of calves to live Salmonella dublin vaccine--a comparison of different serological tests

The serological responses to live Salmonella dublin vaccine was assessed in three groups of calves; three-day-old colostrum-deprived (3DO C-), three-day-old colostrum-fed (3DO C+) and three-month-old (3MO), by the following tests; serum agglutination test (SAT), indirect haemagglutination test (IHA), complement-fixation test (CFT) and antiglobulin test (AGT). Serological activity was detected by all the tests in the 3MO calves. In the 3DO C+ calves no serological activity was detected by either the somatic SAT or IHA but low levels of CF and somatic AGT antibodies were produced. In 3DO C- calves serological activity, often at low levels, was detected by all the tests except the somatic SAT. High levels of flagellar agglutinins were detected in both groups of 3DO calves. It was concluded that with the exception of the flagellar SAT the tests were affected by the age of the calf and in 3DO calves also by the presence of colostral antibodies. However, the use of the SAT in 3MO calves would provide an indication as to the potency of salmonella vaccines.     

Maintenance of long term gamma-herpesvirus B cell latency is dependent on CD40-mediated development of memory B cells

It has been proposed that the gamma-herpesviruses maintain lifelong latency in B cells by gaining entry into the memory B cell pool and taking advantage of host mechanisms for maintaining these cells. We directly tested this hypothesis by kinetically monitoring viral latency in CD40(+) and CD40(-) B cells from CD40(+)CD40(-) mixed bone marrow chimera mice after infection with a murine gamma-herpesvirus, MHV-68. CD40(+) B cells selectively entered germinal centers and differentiated into memory B cells. Importantly, latency was progressively lost in the CD40(-) B cells and preferentially maintained in the long-lived, isotype-switched CD40(+) B cells. These data directly demonstrate viral exploitation of the normal B cell differentiation pathway to maintain latency.     

Rapid identification of yeasts by serological methods: a combined serological and biological method.

A total of 387 yeasts from the contents of the digestive tracts of domestic animals and poultry were identified by slide agglutination tests using factor antisera and urease tests. The results of this serological test were very satisfactory with respect to accuracy and rapidity, particularly when performed in combination with concomitant physiological tests only for assimilation of inositol and potassium nitrate. It may be concluded that such a combination of serological and biological tests is very useful for identifying yeast strains from various sources.     

Basic problems of serological laboratory diagnosis

Serological laboratory diagnosis is inflicted with at least two kinds of basic problems. One type relates to the fact that the serological diagnosis of infectious diseases is double indirect: First, to diagnose an infectious disease, the identification of the microbial agent is sought that caused the disease. Second, to identify this infectious agent, the patient’s immune response to potential agents is measured. So, the serological test is neither measuring directly disease nor the cause of the disease, but the patient’s immune system. Another type of problem is based on the fact that each person’s immune system is very individual. The exact physicochemical properties of antibodies are unique for each clone of antibodies. The way an individual’s immune system sees an infectious agent depends not only on the genetic makeup of the person but also on the personal experience from former encounters with infectious agents. Both types of problems lead to complexities in selecting the appropriate test, in interpreting the results, and in standardizing serological tests. Therefore, a close collaboration of the laboratory with the clinic is mandatory to avoid erroneous conclusions from serological test results, which might lead to wrong decisions in patient care.